Catalina Ecotourism

By Christina Irvin

Catalina Island is a gem located twenty-two miles off the Southern California Coast, and currently has nine protected areas surrounding it. It is part of the Southern California Bite, which, according to the MLPA (1999), provides habitats for at least 1,800 marine species including fish, algae, sea grass, sea turtles, birds, seals, otters, sea lions, dolphins, and invertebrates. The pristine environment is the main attraction for tourists to this island. William Wrigley Jr., the Wrigley’s chewing gum founder, bought the controlling interest of the Santa Catalina Island Company (SCIC) in 1919 with the ultimate goal of preserving the island for all future generations. He envisioned a place for families to enjoy the natural wonders. In 1972, Wrigley’s family established the Catalina Nature Conservancy and donated the land to foster stewardship. The SCIC mission is “committed to preserving the natural beauty and unique character of Santa Catalina Island” (SCIC 2012).

The Wrigley Marine Science Center on Catalina Island viewed from a hillside to the east.

Every year families and researchers alike flock to Catalina to either scuba dive or snorkel the amazing kelp forests and marine world, kayak through deep, clear, blue waters with seals and sea lions, fish for lobster and other species, as well as hike and camp around the island.  Eco-tourism not only supports the Island’s economy but it also inspires the protection of the natural habitats. This industry adds value to preserving the natural aesthetics because it encourages more visitors and greater recreational activity and creates a desire to return. Tourism also develops an awareness of the environmental impacts and the habitats that are at risk. In 2011, the Conservancy created a 20-year master plan, Imagine Catalina: Visions for the Future, with the goal to “look into the future and create a plan of programs and infrastructure improvements that will enable [the Conservancy] to realize the conservation, education and recreation mission over the long term” (Catalina Conservancy 2011).

On March 20th 2012, the Catalina Island Conservancy presented plans to take its first steps following the master plan.  Part of the plan included buying the historic Catherine Hotel in Avalon. The Conservancy’s president, Ann Muscat, hopes that Avalon will provide a welcoming and easily accessible entrance to the Island’s 42,000 acres of nature preserve. This purchase will allow the Conservancy to expand on educational and recreational programs by providing accommodations for eco-tourists, researchers and students. Leslie Baer, the Conservancy’s chief of educational outreach and marketing said, “We’re excited about having a new opportunity to share information about Catalina’s wild places and why the Island is so special as an ecological destination. Our staff and partners are doing groundbreaking conservation and science, and we’re proud to share those stories.”

Unfortunately, some of the Conservancy’s scientists and biologists oppose the upcoming changes because they feel there is greater emphasis on improving the economy than on preserving the local environment and that “conservation is no longer a passion” (Sahagun 2012). Although there is some dissent, the Conservancy has been successful in restoring the Island to its more natural state by minimizing the non-native species and reviving the native species, such as the Catalina Island Fox. The hope is that by providing greater accommodations for eco-tourists and researchers, this kind of success will prosper and that the revenue generated by the Island’s changes will continue to support conservation, eco-tourism, and the appreciation for Catalina’s natural wonders.

After scuba diving in Big Fisherman’s Cove at the USC Wrigley Marine Institute and hiking the local trails, my appreciation for this Island has only grown with each visit. It never ceases to amaze me when I’m swimming through the kelp forests and the sun shines through and highlights the blues and greens under water and magnifies the bright orange of the garibaldi. On another dive, my class-mate Jordan and I spotted an octopus swimming from one rock cave to another and watched its colors change. After an afternoon dive, there is nothing like hiking to the top of a hill overlooking the cove and ocean beyond to watch the sunset. These are the experiences that I hope other tourists encounter and feel the same admiration for this remarkable place. The Imagine Catalina master plan seeks to improve its stewardship through promoting these activities and the Island’s unique, breath- taking beauty.

After just recently diving in Apra Harbor, Guam on Western Shoals Reef, I have an even greater understanding for ecotourism and the importance of supporting ecotourism efforts. Diving through what seem like rolling hills of coral and then coming across huge elephant ear sponges that are only found at this site in Guam are inspiration enough to maintain and promote these areas with such rich and unique biodiversity. Ecotourism draws visitors into these remote and relatively unknown locations where all you see under forty feet of turquoise blue water is an expanse of colorful coral and tropical fish. It is regions like Guam that would truly benefit from the awareness that ecotourism provides.

“About Us.” Visit Catalina Island – The Santa Catalina Island Company. Web. 18 May 2012. http://www.visitcatalinaisland.com.

“Catalina Island Conservancy.” Catalina Island Conservancy. Web. 18 May 2012. http://catalinaconservancy.org.

eCatalina.com. “Conservancy’s ‘Imagine Catalina’ Charts Course for Short Term and Next 20 Years.” eCatalina.com. eCatalina.com/news.

California Department of Fish and Game Resources Agency. 1999. Marine Life Protection Act. http://www.dfg.ca.gov/mlpa

Sahagun, Louis. “Tourism Clashes with Research in Planning Catalina’s Future.” Los Angeles Times 21 Mar. 2012

About the Author: Christina Irvin is a senior environmental studies major from Los Angeles.

Invasive Species Impact on Island Ecology

By Stephen Holle

Planet earth is intimately linked through various modes of transportation such as ships and planes. However, unlikely passengers (flora and fauna) sometimes stroll past security and embark on free rides across the world. The unintended passengers can then become introduced into environments with favorable conditions and limited competition, and the introduced species is able to out compete native flora and fauna. Invasive species are one of the largest threats to biodiversity on a global scale and as a result very few environments are characterized by completely native species. Biogeographic conditions also further compound the issue of nonnative species and islands are especially sensitive to their spread partly due to the limited amount of land surface area, low fecundity, and an absence of coevolution with the invasive species. Therefore, the ecological balance of isolated regions such as Guam is greatly impacted by invasive species, which degrade localized biota (Wiles 2003).

Guam has a number of invasive species which greatly disrupt the ecological balance of the island. However, the brown tree snake (Boiga irregularis) has been one of the most impactful and has decimated native bird populations across the island. B. irregularis was introduced in Guam following World War II and their expansion and growth across the island coincided with a steep decline in native bird populations such as the Marianas Crow and the Island Collared-Dove.

A table depicting the decline of native bird populations on Guam due to the introduction of B. irregularis. Table: Guam Division of Aquatics and Wildlife Resources (Wiles 2003).

However, their destruction was not limited to bird populations and B. irregularis also preyed on lizards, non-native mammals, and flying fox populations. Native bird populations are critical components to the ecology of Guam because they perform valuable functions such as seed dispersal and pollination and when they are absent it greatly disrupts the critically sensitive balance of nature and propagation of native plant species. In order to quantify how detrimental brown tree snakes are to local bird populations the Department of Aquatics and Wildlife Resources (DAWR) on Guam conducted roadside surveys in 11 specific locations on the northern end of the island. In the past Guam has supported approximately 23 native bird species, but since the introduction of the B. irregularis ten of these species were entirely lost from the survey areas and other species experienced a decline around 90%, while others experienced complete extirpation within a short time frame. The eradication of native bird populations occurred rapidly, and within 6.9 years a majority of native bird species experienced significant declines (Wiles 2003).

A photo showcasing a juvenile brown tree snake. Photo credit: Stephen Holle.

In order to conserve natural resources and local conditions, Guam is looking for various ways to control and eradicate B. irregularis populations. On Guam the DAWR has developed a number of mitigation measures such as captive breeding programs and B. irregularis control programs to minimize impacts on the islands ecology. Field workers within DAWR distribute modified minnow traps, which are baited to capture snakes for termination. However, as Diane Vice, director of the brown tree snake control program points out, “the long term goal of the brown tree snake program is eradication, but current technology and staffing needs only allow for population control measures.” Currently, DAWR is focused on controlling outbreaks of B. irregularis on other islands across Micronesia.

A photo depicting modified minnow traps, which are used to capture B. irregularis. Photo credit: Stephen Holle.

DAWR uses trained dogs to inspect cargo entering passenger and commercial planes and ships to curve the export of invasive species like B. irregularis. Other mitigation measures also exist at the federal level and are being developed by the National Wildlife Research Center (a division of the USDA) to control populations of B. irregularis and potentially lead to more effective long term solutions. One application is a biological control in which “toxic mouse bombs”, which are mice laced with the chemical acetaminophen (an active ingredient in aspirin) are dropped out of planes. The brown tree snakes consume the mice and perish by this unsuspecting trap. The chemical is lethal to snake populations, but will not affect other species and humans, which make it a viable control measure. Only time will tell if the mitigation measures are enough to stop this unwelcomed predator and restore baseline conditions (Wiles 2003 & Vice 2012).

Works Cited

Vice, Diane. Personal Interview. 22 May. 2012.

Wiles, Gary et al. “Impacts of the Brown Tree Snake: Patterns of Decline and Species Persistance in Guam’s Avifauna.” Conservation Biology 17 (2003): 1350-1360.

About the Author: Stephen Holle is a senior working toward a bachelor’s degree in environmental studies at USC Dana and David Dornsife College of Letters, Arts and Sciences. With his ENST scientific diving experience he hopes to move on to a career focused on policy and natural resource management.

Economic Effects of the Revised Military Buildup in Guam

By Nick Leonard

Originally published at ScientificAmerican.com

In December 2002, the US–Japan Security Consultative Committee began a series of conversations about strategic military alignment in the Pacific and how to protect their associated countries in “today’s rapidly changing global security environment.” [Guam Buildup EIS, 2010] This three-and-a-half-year conversation evolved into what has been know as the Defense Policy and Review Initiative, part of which planned for the relocation of over 8,600 United States troops from Okinawa, Japan to Guam and other parts of the Pacific.

Map of Guam. Image courtesy of PMEL / NOAA.

However, in response to cuts in the United States’ defense budget, funding for a military build-up in Guam was for a time put on hold as officials tweaked details of the plan, partly with an eye to cost. Recent announcements in early May held prospects of a significant decrease in the number of military personnel to be relocated to Guam in upcoming years—current estimates are at 5000 Marines and 1200 dependents, a decrease of over 40%. In the midst of a global recession and faced with an ever-climbing federal deficit, the United States’ uncertainty is understandable; however, with funding temporarily reduced or frozen and military plans not to be complete until 2015, economic and social consequences of the revised plans for Guam are already being felt throughout that territory. [Kelman, 2012]

Joseph Bradley, Senior Vice President and Economic and Market Statistics Officer for the Bank of Guam, recently spoke to ABC News about the effects of the revised military buildup, stating:

I can’t even begin to tell you how much [Guam has been affected]. There are a number of businesses that had come into Guam in anticipation of the Military Buildup . . . those groups have already pulled out of Guam, walked away . . . because of the delays.

Since we have no idea what will happen in 2015 there is no way to estimate what the future impacts will be.

While some businesses may have “jumped the gun” in terms of development in Guam, there is no doubt the future buildup holds large economic opportunity for residents of this American territory in the South Pacific. Although fewer soldiers will put less stress on this small island than the initial planned 8600, Guam faces complex infrastructure problems to cohesively accommodate the Marines and their dependents. In addition, more military personnel on the island of Guam will likely lead to a larger tourist population and necessitate further development. With infrastructure such as wastewater treatment and electrical generation already in desperate need of upgrades and expansion, the extended timeline on the relocation project and the lack of finality in the plan itself have left numerous questions in the minds of Guam lawmakers about the best pathway for their island’s growth.

First and foremost, Guam is in need of a new wastewater treatment and disposal facility. Regardless of the military buildup, the construction of this critical facility needs to begin in the near future. However, with fewer soldiers stationed on Guam than were initially estimated, plant construction has been delayed as Guam’s local authorities and the military jostle to determine responsibility for funding it. If the new base is constructed at Naval Base Guam, which maintains its own wastewater treatment facility, Guam may be stuck with a $400 million capital investment that will serve as a sunk cost. [Taitano, 2012] However, if the new base is connected with the civilian wastewater treatment center, it is likely the federal government will subsidize a potion of the cost, making the facility more affordable. Either way, this new facility is partially the result of anticipation for the United States military buildup, and it is irresponsible to expect Guam to subsidize military personnel who, when stationed on the island, will represent a jump in population that cannot be handled by the current facilities. [Kelman, 2012]

Similarly, an increase in population and a stronger military presence in Guam will require a larger output from the Guam Power Authority. As stated in the 2010 Draft Environmental Impact Statement:

Currently, Guam has a U.S. Environmental Protection Agency waiver from various Clean Air Act requirements, which allow the use of high sulfur fuels in its electric generation plants.

In an Addendum to this report, the Department of the Navy agreed to help Guam transition to Ultra Low Sulfur Diesel (ULSD) in order to maintain clean, healthful air. This is a step in the right direction for Guam, but it may be an inefficient and wasteful capital investment in the long run.

In March 2008, Guam Bill 166 established a 25% renewable energy goal to be accomplished by 2035. Over the past few years, decreasing costs and larger availability of commercial wind turbines and solar panels have led to talk of large-scale alternative energy production development in Guam. With perfect environmental conditions for wind turbines, the Department of Defense allotted $17 million in the budget for the development of four turbines at the Naval Magazine. Rather than spending excess cash fixing an outdated and commodity-reliant facility, Guam may have larger long-term benefits from further development of wind and solar resources. While land mass may be limited, offshore facilities can be added during the development and dredging of the Apra Harbor, which will be critical to facilitate the docking of aircraft carriers that will arrive under the military’s plan. [Johnson, 2012]

The United States’ uncertainty in the development of Guam has been taxing on the residents, businesses, and utility providers of this small island. Regardless of the number of Marines transferred to Guam, immediate upgrades need to be made to the wastewater treatment facilities and electrical generation plants in order to accommodate increasing numbers of tourists and a growing population. While the scales of the projects are set to undergo review yet again, it should be noted that partial responsibility for this development lies with the United States military. The recent restrictions on federal funds for this development have left the government of Guam pondering ways to pay for such massive projects, which will support not only its residents, but also the military personnel stationed there.

Works Cited:

“Guam Buildup Environmental Impact Statement.” Guam Buildup EIS – Guambuildupeis.us. Environmental Protection Agency, Sept. 2012. Web. 14 May 2012.

Johnson, Tim. “Military Buildup on Guam: Costs and Challenges in Meeting Construction Timelines.” Letter to Hilary Clinton. 27 June 2011. MS. Washington DC.

Kelman, Brett. “GWA: Dededo Base Crucial: Marines Would Justify Federal Funding for Upgrades.” Pacific Daily News. Pacific Daily News, 14 May 2012. Web. 14 May 2012.

Taitano, Zita. “MVariety.com.” Guam Asks US Congress to Authorize Buildup Funding. Marianas Variety, 11 May 2012. Web. 14 May 2012.

“Uncertainty in Guam over Delayed Military Buildup.” Interview by Joseph Bradley. Radio Australia. ABC, 10 May 2012. Web. 14 May 2012.

About the Author: Nick Leonard is a senior in the Marshall School of Business at the University of Southern California. He is minoring in Environmental Studies, and has a keen interest in sustainable aquaculture and marine fisheries.

Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.

Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg,, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.

Entangled in the Excitement of Every New Day

By Nathaniel Kinsey

Originally published at ScientificAmerican.com

Note: By the time this posts the USC Dornsife students, staff and faculty will be in Guam. Immediately before the launch of the expedition the group spent a week at the USC Catalina Campus learning the basics of collecting data along transects as well as intermediate diving skills such as working in two-foot visibility and deeper depths of 65 fsw. The students also attended a lecture and lab on a more advanced science diving topic – collecting fish for aquarium exhibits. Labs in this course can be a bit beyond the ordinary …

Aquarium of the Pacific science diver Chris Plante deploys a barrier net immediately prior to the laboratory exercise on fish collecting. All Photos by Jim Haw.

There I was floating just above the bottom of Big Fishermans Cove helping to untangle a fish from a barrier net. A minute later I successfully hand-netted a juvenile ray and was in the process of untangling him. I released the ray back into the cove to continue on his day; if this was not a practice run he would become the newest exhibit at the Aquarium of the Pacific in Long Beach.

While many recent college graduates are off searching for jobs and stressing about the future, I find myself actively engaged in an activity and learning a skill that a day earlier I had not even knew existed. That is what Environmental Studies 480 has quickly become for me; a new and exciting experience every day.

The barrier net in place.

After a morning dive that consisted of lying transects and doing species surveying with fellow classmate Katie Graves, it was off to a pre-lunch lecture. This lecture was by science diver Chris Plante, Assistant Curator for the Aquarium of the Pacific and an expert in species collection for aquarium exhibit. His lecture was on the basics of fish and invertebrate collection.

This crash course included the what, where, why and who of collection, and equipment used. The main focus of the lecture was centered on fish collection because each species of fish presents its own challenge. The various techniques used for collection of fish included: hook and line fishing, hand nets, beach seines, and barrier nets.

Chris argued that the preferred means of collection was generally a combination of hand nets and barrier. Hand nets come in two forms: monofilament and nylon. Monofilament nets are less visible to the highly aware fish, and quicker in the water. Nylon nets come in various colors that can be helpful for camouflage, but are significantly slower than monofilaments.

A juvenile ray in a hand net.

Barrier nets are large nets that range in size from a few feet up to twenty feet that are suspended in the water for fish to become entangled in. This information was all new to me and I thoroughly enjoyed the lecture. The best part came at the end of lecture when Chris, along with my professors, confirmed that we would be practicing these techniques in an afternoon dive.

After lunch it was time to try my hand at fish collection. The plan was for groups of eight divers each, all with hand nets, to drive fish into a set-up barrier net. Placed into group two, I had to wait for the opportunity to net my own fish. Group two’s turn came, I quickly kicked out to the drop down location.

Descending under the surface, I dropped into a forest of kelp then proceeded to drive fish forward into the barrier net. Coming around to the other side I saw that a few small fish had become entangled in the net.

The author driving fish toward the barrier net with hand net at the ready.

Watching Chris untangle a few other fish I had an opportunity of my own. The experience was extremely rewarding, and I cannot imagine that this sort of laboratory is available in many other universities. With this only being day three of a three-week Maymester program I cannot wait for my next teachable moment.

About the Author: Nathaniel Kinsey just graduated from USC with a Bachelor of Science in Environmental Studies. He is accepted into the USC Progressive Degree for fall of 2012 where he will be pursuing his Master of Arts in Environmental Studies. He hopes to pursue a career in either watershed management or sustainable cities.

Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.

Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg,, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.

The Navy Dive Tables

By Kaitlin Mogentale

Originally published at ScientificAmerican.com

If you asked me what my greatest fear is while scuba diving, I wouldn’t hesitate with my answer– the bends. The bends, or decompression sickness (DCS), is a decompression illness arising from the dangers of breathing compressed air at depth for prolonged periods, coupled with improper decompression or excessively rapid ascents.

A photo of the Catalina Hyperbaric Chamber, where bent divers are sent for treatment (Photo by Kaitlin Mogentale).

The most severe of symptoms are permanent CNS damage, and occasionally death. The dangers of improperly off-gassing after a dive have been (rightfully) drilled into my head during the prerequisite ENST-298 Introduction to Scientific Diving class.

In class we studied Haldane’s 1908 report on compressed-air illness to better understand decompression sickness. From Haldane’s research came an initial 2:1 rule. The rule states that so long as a diver remains within the ratio of 2:1 for the pressure at depth versus ambient pressure on ascent, he is safe to ascend without developing a case of DCS–although it is important to note that due to complex human physiology, there is no definitive point between avoiding and getting DCS.

Later extensive research at the U.S. Navy Experimental Diving Unit (NEDU) by Dwyer, Hawkins, Workman, Yarborough, and others from the 1930s-1960s arrived at more precise ratios using empirical data, focusing on the pressure of the inert gas in air directly involved in DCS, nitrogen. Workman’s model introduced M-Values (or greatest partial pressure of nitrogen a “tissue” compartment can tolerate without the onset of DCS at a given absolute pressure) for each of 6 designated hypothetical tissue compartments with 5, 10, 20, 30, 40, 80, and 120-minute nitrogen half-times. These 6 compartment half-times were calculated based on the capacity of the “tissue” to store nitrogen gas, and the effectiveness of nitrogen transport to and from the tissue, such that:

Half-time= (1/c) x S/C,                                                                       (1)

where c is a constant of proportionality, C is equivalent to gas transport effectiveness, and S is the solubility coefficient for the gas in a tissue. A fast tissue with a short half-time corresponds to a well-perfused tissue, and perhaps lower fat content, as nitrogen is less soluble in aqueous tissues than in fatty tissues.

Haldane calculated the 5, 10, 20, 40, and 75 half-times used in his model based on their representation of what he theorized happens in the body. Haldane hypothesized men became fully saturated with nitrogen in 5 hours and that additional nitrogen loading after 4 half-times “would scarcely be appreciable”. The final 75 minute “tissue” compartment therefore corresponds to the fact that 4 x 75 minutes = 300 minutes, or 5 hours. The Navy Tables use Haldane’s calculations as the basis for their theoretical compartments, changing the 75-minute compartment to 80 minutes and adding a 120-minute compartment. The Navy assumed 6 half-times for saturation. The changes reflected problems associated with earlier US Navy tables that had used Haldane’s original five compartments in their calculation.

Workman’s M-values are based on a compartment’s nitrogen half-time and the pressure of the breathing gas, which is always dependent on depth. M-values are mathematically represented by the equation

M= Mo + ∆Md,                                                                                     (2)

where M is the nitrogen partial pressure limit for each compartment, Mo is the partial pressure of nitrogen tolerated at sea level, defined for each compartment, and ∆Md is the increase of M with increasing depth, defined for each compartment, multiplied by the depth (in feet of sea water).

One simply divides the given compartment’s M-Value by the ambient pressure at sea-level to arrive at the permissible nitrogen pressure surfacing ratio, which is not constant across all compartments as Haldane assumed.

The studies done at NEDU over the decades discovered that faster compartments tolerate a much higher nitrogen pressure gradient than can the slower compartments. This difference can be accounted for in the greater solubility of nitrogen in slower tissues (or a low transport efficiency in those tissues), resulting in a greater molar concentration of nitrogen than the fast tissues. This is why model compartments representing slower tissues feature more conservative M-values and ratios than those representing faster tissues. Slower tissues “hold onto” their nitrogen longer which places them at an increased risk for bubble formation. The M-values are called “sliding scale M-values”–each compartment has a distinct M-value at any given ambient pressure.

We will be focusing on no-decompression dives during the span of the ENST-480 course, so I will focus on using the Navy Dive Tables with no-decompression. M-values can be used to determine the maximum amount of bottom time that can be allotted at a certain depth without requiring decompression stops. For this type of calculation, the planned depth is converted to absolute pressure in feet seawater (fsw) and the partial pressure of nitrogen is calculated. If the M0-value for a compartment happens to be less than the absolute nitrogen pressure in fsw at that depth, the diver would use the following equation to determine the No-Decompression Limit (NDL on the Navy dive tables, or max bottom time without required decompression) for the dive:

t= [T/ln(2)] x ln[(P0-Pa)/(Pm-Pa)]                                                 (3)

where t= a compartment’s maximum time at the planned depth, T= the half-life (in minutes) of the specific compartment, Po= initial nitrogen partial pressure in the compartment (at the surface at the start of the dive), Pa= ambient nitrogen pressure at the planned depth, and Pm= the M-value for the specific compartment allowed at the surface (or M0).

Once the NDL is calculated for each compartment, the one with the shortest time becomes the controlling compartment at that depth. The dive must not exceed the controlling compartment’s NDL at that depth to avoid required decompression stops. The Navy Tables round NDL’s down to the nearest 5 or 10 minutes, for easier memorization.

Pressure Groups and Repetitive Dives

After a dive, there is a certain amount of nitrogen left over in the various compartments (called residual nitrogen). With proper off-gassing, remnant nitrogen is not problematic to the surfaced diver. Residual nitrogen becomes important when a diver is conducting a repetitive dive.

Any dive completed within 12 hours of a previous dive is considered a repetitive dive. 12 hours has significance as the elapsed time before the slowest 120-min compartment is 98% de-saturated with excess nitrogen (the equivalent of 6 half-times). The Navy Tables use the 120-min compartment to track residual nitrogen. That is, the 120-min is the controlling compartment for determining the entering pressure group on a repetitive dive. Pressure groups are based on intervals of total air pressure in the controlling 120-min compartment. The total air pressure in the compartment is determined by

A(t)= Aa + (Aa – A0)e-kt,                                                                  (4)

such that A(t)= total air pressure in the compartment, Aa= total ambient pressure, A0= initial load in the compartment. k is a constant determined by the half-life of the compartment, using the equation

k=ln(2)/T.                                                                                                (5)

In the case of the 120-min compartment, T would be 120, and k subsequently becomes 0.00578.

Using equation 4, the total air pressure in the 120-min compartment after a dive of given length and depth can be calculated. The pressure groups are designated by a letter, A-Z, and are identified by a range of total air pressure determined by the Navy. For example, the pressure group with the letter A corresponds to a range of total pressure in the 120-min compartment equivalent to 33-35 fsw. As the letters get closer to Z, the total pressure in the compartment gets higher. The entering pressure group for a repetitive dive determines the maximum bottom time for that repetitive dive, while taking into account the residual nitrogen time from previous dives.

Let’s use these equations to show standard dive table calculations:

A diver wants to complete a dive to 35 feet, without any required decompression. At 35 fsw, nitrogen partial pressure is 0.79 x (33+35)= 53.72 fsw. Compartments 5, 10, 20, and 40 can withstand pressure loading up to 104, 88, 72, and 58 fsw of nitrogen respectively (these are their M0-values). The 80-min and 120-min compartments have M-values less than 53.72, (52 and 51 fsw respectively) and therefore a diver can remain at that depth for only a limited amount of time until a decompression stop is required. Using equation 3, we can determine the maximum amount of time a diver can remain at that depth without required decompression for each of the 2 slow compartments.

t= [T/ln(2)] x ln[(Po-Pa)/(Pm-Pa)]

For the 80-min tissue compartment, t=320.8 minutes

For the 120-min tissue compartment, t=401.9 minutes.

In this case, the 80-min compartment is the controlling compartment. This means that the diver can stay at 35 feet for a max of 320.8 minutes without any required decompression (the US Navy Tables round this down to 310 minutes).

So let’s say our diver acquires a bottom time of 40 minutes at 35 feet.

Using depth equivalent pressures, A0= 33 fsw, k= ln(2)/120, Aa=33 fsw + the planned depth of 35 fsw=68, and t=40 minutes.

Crunching these numbers, we see that the diver exits the water with A(t)= 40 fsw, placing him or her in pressure group D. After some time on the surface (the diver’s surface interval time or SIT), the diver will continue to off-gas and can enter a repetitive dive at a pressure group lower than D. Using this information, a diver can determine the maximum NDL for the next dive using equation 3, incorporating the residual nitrogen into the initial nitrogen load.

Kaitlin Mogentale stands in front of the Catalina Hyperbaric Chamber hanger.

The NAUI dive tables we use are much more conservative than the Navy Dive Tables but are largely based off of the Navy’s basic calculations and conclusions. It is important to understand the mathematics and science behind the Navy Tables in order to understand the NAUI tables.

Author Bio: Kaitlin Mogentale is a freshman at USC pursuing a B.A. in Environmental Studies. She also looks to complete minors in Urban Policy & Planning and Spanish. She plans to use her interest and knowledge in the field of environmental science to serve as an advocate for businesses and developers, focusing on the importance and pertinence of environmentally sound practices.

Sources Cited:

Acott, C. J. “Testing JS Haldane’s decompression model.” Journal of the South Pacific Underwater Medicine Society (2000). Rubicon Foundation.Web. 15 May 2012.

Anderson, Marlow. “The Mathematics of the Navy Dive Tables.” The Physics of Scuba Diving. Nottingham, UK: Nottingham University Press, 2011. 137-46. Print.

Baker, Erik C., P.E. Understanding M-values. Scuba Diving- New Jersey and Long Island New York. Web. 13 May 2012.

Huggins, Karl E. The Dynamics of Decompression Workbook. Ann Arbor, Michigan: The University of Michigan, 1992. Print.

Workman, R. D. Calculation of Decompression Schedules for Nitrogen-Oxygen and Helium-Oxygen Dives. Washington D.C. : U.S. Navy Experimental Diving Unit, 1965. Defense Technical Information Center. Web. 13 May 2012.

Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.

Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg,, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.

Marine Ecosystem Based Management

By Nathaniel Kinsey

Originally published at ScientificAmerican.com

Marine ecosystem-based management (EBM) goes beyond politically drawn lines and looks at the many factors that go into effective natural resource management. For example, marine ecosystems offer human society many services providing food, fuel, mineral resources, and even pharmaceuticals. These services are of high anthropogenic value and the hope of EBM is that it offers a holistic approach that can properly balance the demand on the ecosystem in a beneficial way. The holistic approach according to COMPASS, a team of science based communication professionals that work to communicate science at the policy creation point, includes the integration of “ Ecological, social, economic, and institutional perspectives, recognizing their strong interdependences” (COMPASS Scientists 2005).

Map of East Pacific Ocean Currents including the Aleutian Current, California Current, and Central Pacific Gyre. Source: Dr. Elizabeth Turner / NOAA.

Effective EBM strategies are currently being implemented among ecosystems within the California Current (see map). The California Current is known for strong seasonal upwelling that is influenced by two climate factors: the El Niño Southern Oscillation and the Pacific Decadal Oscillation. These areas of upwelling are recognized as areas of high biodiversity and have high ecosystem value, thus it makes sense to set the best system too properly manage the natural resources found there.

Nevertheless, there are several challenges that face EBM implementation. The first of these is clearly defining a vision and a list of objectives for the ecosystem. As many ecosystems cover large regional areas, like the California Current, there are many stakeholders involved in the management. For example while the states of Washington, Oregon and California have a governors’ agreement to work together on marine EBM implementation; they still face many differing coastal laws, political influences and environmental opinions. It will be sometimes be difficult for states to agree upon a list of common goals and objectives for the marine EBM. The second challenge is the lack of a national ocean governance policy framework. Ocean resources are managed by various organizations at the federal and state level. These agencies and organizations will have to cooperate effectively, which has proven to be difficult. Lastly, there are few examples of fully implemented marine ecosystem-based plans and their results. This lack of proven examples for this management style means that stakeholders are taking a risk by supporting the costly process of establishing marine EBMs (Leslie & Mcleod, 2007).

Author photo by Jim Haw.

The task of establishing a marine EBM is a challenge, which at the very least requires cooperation at the state and federal levels of government, as well as stakeholder groups. Despite these challenges, the promise of effective marine ecosystem-based management strategies could provide a more sustainable, more economically prosperous future.

About the author: Nathaniel Kinsey recently graduated from the USC Dana and David Dornsife College of Letters, Arts and Science with a BS in Environmental Studies. In Fall 2012, he will begin a Progressive Master’s Degree in the USC Environmental Studies Program where he will focus his studies on watershed conservation and management.

Sources:

COMPASS Scientists. (2005, March 21). Scientific consensus statement on marine ecosystem-based management. NOAA.

Leslie, H., & McLeod, K. (2007 ). Confronting the challenges of implementing of marine ecosystem-based managemnent. Frontiers in Ecological and the Environment , 5(10), 3-4.

Turner , E. (2011, February 16). U.S. global ocean ecosystems dynamics (globec) northeast pacific.

Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.

Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg,, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.

The Ordot Dump and Layon Landfill

By Nicole Matthews

Originally published at ScientificAmerican.com

Solid waste disposal is a major environmental issue faced by countries around the world. For small islands such as Guam the problems that come with solid waste disposal are especially demanding due to the limited amount of space available and the close proximity to bodies of water that flow into the ocean.

One dumpsite that has been a consistent source of pollution is the Ordot Dump. First used by the Japanese during their occupation of Guam in World War II, the dump was a consistent source of environmental pollution until its closure in 2008. In fact, it was not until 45 years after its initial use that the dump was marked as harmful to the environment under the Clean Water Act of 1972.

Map of various dumping and recycling sites on Guam. Source: www.guamsolidwastereceiver.org

Specifically, in 1986, it was discovered that the Ordot Dump was leaking leachate, water that seeps through the solid waste and collects the chemical compounds it comes in contact with. This leachate was seeping into Pago Bay, one of the major sources of drinking water for the island’s inhabitants.

Recognizing the potential health impacts presented by the dump, the Guam Department of Public Works (GDPW) was ordered to shut down the Ordot facility and replace it with an alternate site, as well as implement a progressive waste disposal/recycling system. A new site was chosen, and the Layon Landfill was constructed within four years. Although a relatively short-term solution, the Layon site is estimated to have a capacity that will serve the inhabitants of Guam for thirty years.

The Layon Landfill contains a double liner system with a built in leak detection. Such preventive technologies serve to eliminate groundwater contamination and gas release (due to anaerobic decomposition of waste materials) from the site. Although the Layon Landfill closely follows EPA regulations, there is never an absolute guarantee that harmful contaminants will not be released into the surrounding environment. For example, the risk of sedimentary and groundwater contamination, as well as methane release is still a possibility.

Author photo by Jim Haw.

The issues faced by Guam regarding the two landfills pose questions for other island nations facing waste disposal issues. The Layon Landfill represents a temporary fix to a critical long-term problem. It will be interesting to see what kinds of solutions other island communities develop in the future.

Author Bio: Nicole Matthews is a freshman working toward a bachelor’s degree in Political Science in the USC Dana and David Dornsife College. After graduating, she plans to pursue a graduate degree in environmental law and policy.

References:

Delfin, Joanna. “Environmental Story: History of the Ordot Dump.” Guambusinessmagazine.com. Guam Business Magazine, May 2012. Web. 9 May 2012.

“Ordot Dump and Layon Landfill.” Guamsolidwastereceiver.org. Gersham, Brickner, & Bratton, Inc., 2012. Web. 8 May 2012.

Editor’s note: Scientific Research Diving at USC Dornsife is offered as part of an experiential summer program offered to undergraduate students of the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island and throughout Micronesia. Students investigate important environmental issues such as ecologically sustainable development, fisheries management, protected-area planning and assessment, and human health issues. During the course of the program, the student team will dive and collect data to support conservation and management strategies to protect the fragile coral reefs of Guam and Palau in Micronesia.

Instructors for the course include Jim Haw, Director of the Environmental Studies Program in USC Dornsife, Assistant Professor of Environmental Studies David Ginsburg,, SCUBA instructor and volunteer in the USC Scientific Diving Program Tom Carr and USC Dive Safety Officer Gerry Smith of the USC Wrigley Institute for Environmental Studies.