Marine debris accumulation in the nearshore marine habitat of the endangered Hawaiian monk seal, Monachus schauinslandi 1999-2001

Large amounts of marine debris are present in shallow reefs adjacent to beach haulouts of the critically endangered Hawaiian monk seal, Monachus schauinslandi. These areas serve as seal pup nurseries, and injury and death caused by entanglement in marine debris are undermining population recovery efforts. We investigated the extent of this threat by measuring the accumulation of potentially entangling derelict fishing gear in nursery zones, 1999-2001. Plots of reef 1.0-1.3 km2 at three Northwestern Hawaiian Islands were initially cleaned of derelict fishing gear in 1999 then resurveyed in 2000 and 2001. Submerged debris densities across sites ranged from 16 to 165 debris items/km2. Resurveyed sites yielded annual marine debris accumulation rates from 0 to 141 debris items/km2. This large range was attributed to the physiography of reef areas surveyed. Trawl net webbing was significantly more common than other types of debris recovered and represented 84% of all debris encountered, suggesting that much of the debris originated from distant North Pacific Ocean fisheries. The likely source of most debris is the multinational trawl fisheries of the North Pacific Ocean. An international solution to this problem is needed. Targeted marine debris removal is a short-term, successful, entanglement mitigation strategy.     

Derelict fishing gear in the northwestern Hawaiian Islands: diving surveys and debris removal in 1999 confirm threat to coral reef ecosystems

Marine debris threatens Northwestern Hawaiian Islands' (NWHI) coral reef ecosystems. Debris, a contaminant, entangles and kills endangered Hawaiian monk seals (Monachus schauinslandi), coral, and other wildlife. We describe a novel multi-agency effort using divers to systematically survey and remove derelict fishing gear from two NWHI in 1999. 14 t of derelict fishing gear were removed and debris distribution, density, type and fouling level documented at Lisianski Island and Pearl and Hermes Atoll. Reef debris density ranged from 3.4 to 62.2 items/km². Trawl netting was the most frequent debris type encountered (88%) and represented the greatest debris component recovered by weight (35%), followed by monofilament gillnet (34%), and maritime line (23%). Most debris recovered, 72%, had light or no fouling, suggesting debris may have short oceanic circulation histories. Our study demonstrates that derelict fishing gear poses a persistent threat to the coral reef ecosystems of the Hawaiian Archipelago.     

On North Pacific circulation and associated marine debris concentration

Marine debris in the oceanic realm is an ecological concern, and many forms of marine debris negatively affect marine life. Previous observations and modeling results suggest that marine debris occurs in greater concentrations within specific regions in the North Pacific Ocean, such as the Subtropical Convergence Zone and eastern and western "Garbage Patches". Here we review the major circulation patterns and oceanographic convergence zones in the North Pacific, and discuss logical mechanisms for regional marine debris concentration, transport, and retention. We also present examples of meso- and large-scale spatial variability in the North Pacific, and discuss their relationship to marine debris concentration. These include mesoscale features such as eddy fields in the Subtropical Frontal Zone and the Kuroshio Extension Recirculation Gyre, and interannual to decadal climate events such as El Ni?o and the Pacific Decadal Oscillation/North Pacific Gyre Oscillation.     

Marine debris accumulation in the Northwestern Hawaiian Islands: an examination of rates and processes

Large amounts of derelict fishing gear accumulate and cause damage to shallow coral reefs of the Northwestern Hawaiian Islands (NWHI). To facilitate maintenance of reefs cleaned during 1996-2005 removal efforts, we identify likely high-density debris areas by assessing reef characteristics (depth, benthic habitat type, and energy regime) that influence sub-regional debris accumulation. Previously cleaned backreef and lagoonal reefs at two NWHI locations were resurveyed for accumulated debris using two survey methods. Accumulated debris densities and weights were found to be greater in lagoonal reef areas. Sample weight-based debris densities are extrapolated to similar habitats throughout the NWHI using a spatial 'net habitat' dataset created by generalizing IKONOS satellite derivatives for depth and habitat classification. Prediction accuracy for this dataset is tested using historical debris point data. Annual NWHI debris accumulation is estimated to be 52.0 metric tonnes. For planning purposes, individual NWHI atolls/reefs are allotted a proportion of this total.     

How multiagency partnerships can successfully address large-scale pollution problems: a Hawaii case study

Oceanic circulation patterns deposit significant amounts of marine pollution, including derelict fishing gear from North Pacific Ocean fisheries, in the Hawaiian Archipelago [Mar. Pollut. Bull. 42(12) (2001) 1301]. Management responsibility for these islands and their associated natural resources is shared by several government authorities. Non-governmental organizations (NGOs) and private industry also have interests in the archipelago. Since the marine debris problem in this region is too large for any single agency to manage, a multiagency marine debris working group (group) was established in 1998 to improve marine debris mitigation in Hawaii. To date, 16 federal, state, and local agencies, working with industry and NGOs, have removed 195 tons of derelict fishing gear from the Northwestern Hawaiian Islands. This review details the evolution of the partnership, notes its challenges and rewards, and advocates its continued use as an effective resource management tool.     

Pelagic microplastics around an archipelago of the Equatorial Atlantic

Plastic marine debris is presently widely recognised as an important environmental pollutant. Such debris is reported in every habitat of the oceans, from urban tourist beaches to remote islands and from the ocean surface to submarine canyons, and is found buried and deposited on sandy and cobble beaches. Plastic marine debris varies from micrometres to several metres in length and is potentially ingested by animals of every level of the marine food web. Here, we show that synthetic polymers are present in subsurface plankton samples around Saint Peter and Saint Paul Archipelago in the Equatorial Atlantic Ocean. To explain the distribution of microplastics around the Archipelago, we proposed a generalised linear model (GLM) that suggests the existence of an outward gradient of mean plastic-particle densities. Plastic items can be autochthonous or transported over large oceanic distances. One probable source is the small but persistent fishing fleet using the area.     

Marine debris collects within the North Pacific Subtropical Convergence Zone

Floating marine debris, particularly derelict fishing gear, is a hazard to fish, marine mammals, turtles, sea birds, coral reefs, and even human activities. To ameliorate the economic and environmental impact of marine debris, we need to efficiently locate and retrieve dangerous debris at sea. Guided by satellite-derived information, we made four flights north of Hawaii in March and April 2005. During these aerial surveys, we observed over 1800 individual pieces of debris, including 122 derelict fishing nets. The largest debris concentrations were found just north of the North Pacific Transition Zone Chlorophyll Front (TZCF) within the North Pacific Subtropical Convergence Zone (STCZ). Debris densities were significantly correlated with sea-surface temperature (SST), chlorophyll-a concentration (Chla), and the gradient of Chla. A Debris Estimated Likelihood Index (DELI) was developed to predict where high concentrations of debris would be most likely in the North Pacific during spring and early summer.     

A pre- and post-MARPOL Annex V summary of Hawaiian monk seal entanglements and marine debris accumulation in the northwestern Hawaiian Islands, 1982-1998

Entanglements of Hawaiian monk seals, Monachus schauinslandi, were documented in the northwestern Hawaiian Islands (NWHI) from 1982 to 1998, and debris which presented a threat of entanglement was inventoried and removed from 1987 to 1996. A total of 173 entanglements was documented. The number of entanglements did not change after implementation of MARPOL Annex V in 1989. Pups and juvenile seals were more likely to become entangled than older seals, and became entangled primarily in nets, whereas entanglement of subadults and adults was more likely to involve line. The subpopulation of seals at Lisianski Island experienced the most entanglements, although Lisianski did not accumulate the most debris. Localized high entanglement rates may gravely affect individual monk seal subpopulations. Accumulation of debris has not diminished since implementation of Annex V, nor has occurrence of derelict drift nets abated since a 1989 moratorium. Debris washing ashore has likely been circulating in the North Pacific Ocean for some time.     

At-sea detection of derelict fishing gear in the North Pacific: an overview

There are numerous known impacts of derelict fishing gear (DFG) to marine ecosystems and safe navigation around the world. To mitigate these impacts, the preemptive detection and removal of DFG at sea are being pursued. This special issue focuses on the North Pacific Ocean because of historic and ongoing research on DFG in the area, particularly as it relates to the Hawaiian Archipelago. In order to develop an effective detection strategy, information and expertise from three disciplines must be integrated: marine debris, oceanography, and remote sensing technology. Building upon results and discussions during a workshop held in December 2008, this special issue provides both results of original research and review papers, pursuing each discipline as it relates to DFG and outlining a multi-faceted strategy to effectively detect DFG at sea. This strategy serves as a roadmap, taking us closer to realizing the goal of detecting and removing DFG at sea.     

Creating a GIS-based model of marine debris "hot spots" to improve efficiency of a lobster trap debris removal program

Debris removal programs are combatting the accumulation of derelict fishing gear and other debris in marine habitats. We analyzed 5 years of lobster trap debris removal data in Biscayne National Park, Florida to assess removal efficiency and develop spatially-explicit mapping tools to guide future removals. We generated and validated debris "hot spots" maps that combined remotely-sensed data (i.e. benthic habitat type and bathymetry) with 862 locations of previous debris collection. Our hot spot models spatially depict regions of likely debris accumulation, reducing the search area by 95% (from 332 km(2) to 18 km(2)) and encompassing 100% of the validation sites. Our analyses indicate removal contractors using sub-surface towed divers enhanced debris recovery. Additionally, the quantity of debris removed did not decrease with increased efforts, suggesting that debris supply in situ exceeds removal efforts. We conclude with the importance of coupling analysis of ongoing debris removal programs with GIS technology to improve removal efforts.     

Impacts of marine debris on wild animals in the coastal area of Korea

Over the last decade, marine debris has become a major factor affecting the coastal ecosystem of Korea. This study compiled information regarding how marine debris impacts wildlife in Korea. Cases of marine debris impacting wildlife were collected from experts of various fields and from local participants through an open access website from February 2010 to March 2012. A total of 21 species were affected by marine debris: 18 species of birds, 2 species of mammals, and 1 species of crustacean. Five threatened or protected species were identified: black-faced spoonbill, finless porpoise, water deer, whooper swan, and greater painted snipe. Recreational fishing gears were the types of debris that most frequently impacted wildlife, especially birds. Black tailed gulls were the most vulnerable species to recreational fishing hooks and lines. Although it was preliminary, this study revealed that recreational fishing activities should be prioritized when managing marine debris in Korea.     

Baseline for beached marine debris on Sand Island, Midway Atoll

Baseline measurements were made of the amount and weight of beached marine debris on Sand Island, Midway Atoll, June 2008-July 2010. On 23 surveys, 32,696 total debris objects (identifiable items and pieces) were collected; total weight was 740.4 kg. Seventy-two percent of the total was pieces; 91% of the pieces were made of plastic materials. Pieces were composed primarily of polyethylene and polypropylene. Identifiable items were 28% of the total; 88% of the identifiable items were in the fishing/aquaculture/shipping-related and beverage/household products-related categories. Identifiable items were lowest during April-August, while pieces were at their lowest during June-August. Sites facing the North Pacific Gyre received the most debris and proportionately more pieces. More debris tended to be found on Sand Island when the Subtropical Convergence Zone was closer to the Atoll. This information can be used for potential mitigation and to understand the impacts of large-scale events such as the 2011 Japanese tsunami.     

Geodynamic model of the evolution of the Pacific Ocean

The present Pacific Ocean differs significantly in its structure and evolution from the expanding Atlantic Ocean. The Pacific is asymmetric. Its mid-ocean ridge is located not along its median line but is closer to South America and adjoins North America. The Pacific is surrounded by a ring of subduction zones but has marginal seas only at its Eurasian margins. After the breakup of Pangea, the Atlantic began to open and the Pacific began to close. This paper examines the evolution of the Pacific Ocean and, in particular, the formation mechanisms of its present structures. Numerical modeling of the long-term drift of a large continent is performed, with the initial position of the continent corresponding to the state after the breakup of the supercontinent. At first the continent, driven by the nearest descending mantle flow, begins to approach a subduction zone. Since the mantle flows beneath a large continent have different directions, its velocity is a few times lower than that of the mantle flows near the subduction zone. As a result, a zone of extension arises at the active continental margin and a fragment is broken off from the continent; this fragment rapidly moves away and stops above the descending mantle flow as in a trap. A marginal sea forms at the active continental margin. The continent continues its slow movement toward the subduction zone. The oceanic lithosphere, which earlier sank vertically, begins to descend obliquely. This evolutionary stage corresponds to the present position of Eurasia. The modeling shows how the interaction of the continent with the mantle causes the subduction zone to roll back toward the ocean. Subsequently, the continent nevertheless catches up with the subduction zone, and they move together for a while. The marginal sea then closes and high compressive stresses arise at the active continental margin. This state corresponds to the present position of South America. During the subsequent drift, the continent together with the subduction zone reaches the mid-ocean ridge and partially overrides it. This state corresponds to North America, which was the first to break off from Pangea and passed through the stages of both Eurasia and South America. The large and slowly moving Eurasia, which formed only at the time of Pangea, is still in the first evolutionary stage of the Pacific Ocean closure.     

Trends and drivers of marine debris on the Atlantic coast of the United States 1997-2007

For the first time, we documented regional differences in amounts and long-term trends of marine debris along the US Atlantic coast. The Southeast Atlantic had low land-based and general-source debris loads as well as no increases despite a 19% increase in coastal population. The Northeast (8% population increase) also had low land-based and general-source debris loads and no increases. The Mid-Atlantic (10% population increase) fared the worst, with heavy land-based and general-source debris loads that increased over time. Ocean-based debris did not change in the Northeast where the fishery is relatively stable; it declined over the Mid-Atlantic and Southeast and was correlated with declining regional fisheries. Drivers, including human population, land use status, fishing activity, and oceanic current systems, had complex relationships with debris loads at local and regional scales. Management challenges remain undeniably large but solid information from long-term programs is one key to addressing this pressing pollution issue.     

Marine debris surveys at Volunteer Beach, Falkland Islands, during the summer of 2001/02

This survey evaluated the monthly accumulation rate of marine debris and the types of objects washed ashore at Volunteer Beach on East Falkland between October 2001 and March 2002. The mean (±SD) accumulation rate of marine debris was 77 ± 25 items/km/month, of a mean weight of 17.3 ± 12 kg. Forty different objects were collected and the five most frequent items were cotton fabric, string, polystyrene packing sheet, plastic packing tape and broken plastic pieces. The debris on Volunteer Beach was dominated by fishing debris; 42% of the items were discarded fishing equipment, while 39% of the items were of a packaging or associated nature. The mostly likely source of this household waste was fishing vessels, with Falkland Islands Government (FIG) fisheries observers seeing 27 of the 40 items of debris collected from Volunteer Beach being discarded from fishing vessels. It is suggested that, although further marine debris research is warranted, more effective at-sea ship waste disposal regulations are required in Falkland waters to reduce environmental and economic threats both at the local and international level.     

Prevalence and composition of fishing gear debris in the nests of northern gannets (Morus bassanus) are related to fishing effort

Bycatch and indirect mortality associated with global fishing operations affect non-target species. Northern gannets (Morus bassanus) and other seabirds incorporate marine debris, much of it originating in fisheries, into their nests, at times resulting in entanglement. We compared the prevalence and composition of marine debris in nests at two gannet colonies in Newfoundland before and after a basin-wide ground fish closure in 1992, and at the species' largest colony in the Gulf of St. Lawrence, where fishing effort is low. The proportion of nests with marine debris decreased following the fishery closure, and the proportion of nests with fishing gear was related exponentially to the number of gillnets set around breeding colonies. Assessing the composition of gannet nests could provide a useful index of the prevalence of fishing debris and could be used to assess entanglement risk of other animals in the marine environment over decadal scales.     

Strategy for mitigation of marine debris: Analysis of sources and composition of marine debris in northern Taiwan

Six sites (two sites for each of rocky shores, sandy beaches, and fishing ports) in northern Taiwan were selected to investigate the amount and density of marine debris in each of the four seasons and after spring and neap tides from 2012 to 2013. The results indicate that marine debris was higher on rocky shores than sandy beaches and fishing ports. There is no significant difference between season and tide. The dominant debris was plastic-type, followed by polystyrene. The majority of debris originated from recreational activities, followed from ocean/waterway activities. The results suggest that the following actions are needed: (1) continue and reinforce the plastic-limit policy; (2) increase the cleaning frequency at rocky shores; (3) promote marine environmental education, with a goal of debris-free coasts; (4) recycle fishing gear and to turn that gear into energy; and (5) coordinate between agencies to establish a mechanism to monitor debris.     

Floating marine debris surface drift: Convergence and accumulation toward the South Pacific subtropical gyre

Whatever its origin is, a floating particle at the sea surface is advected by ocean currents. Surface currents could be derived from in situ observations or combined with satellite data. For a better resolution in time and space, we use satellite-derived sea-surface height and wind stress fields with a 1/3° grid from 1993 to 2001 to determine the surface circulation of the South Pacific Ocean. Surface currents are then used to compute the Lagrangian trajectories of floating debris. Results show an accumulation of the debris in the eastern-centre region of the South Pacific subtropical gyre ([120°W; 80°W]–[20°S; 40°S]), resulting from a three-step process: in the first two years, mostly forced by Ekman drift, the debris drift towards the tropical convergence zone (30°S). Then they are advected eastward mostly forced by geostrophic currents. They finally reach the eastern-centre region of the South Pacific subtropical gyre from where they could not escape.     

The incentive program for fishermen to collect marine debris in Korea

A significant amount of sea-based marine debris is generated and deposited in Korean coastal waters. The Korean government has removed 66,000 tons of deposited marine debris since 1999. However, to fully address the problem, the generation of marine debris needs to be prevented. As an alternative, Korean government has initiated an incentive program for fishermen, who collect fishing gear or other marine debris while fishing. Although a considerable amount of marine debris is collected and removed from major fishing grounds, the program may not incentivize long-term sustainable behavior, resulting in further discarding of marine debris when the program is completed.     

Physical and chemical effects of ingested plastic debris on short-tailed shearwaters, Puffinus tenuirostris, in the North Pacific Ocean

We investigated the plastics ingested by short-tailed shearwaters, Puffinus tenuirostris, that were accidentally caught during experimental fishing in the North Pacific Ocean in 2003 and 2005. The mean mass of plastics found in the stomach was 0.23 g per bird (n = 99). Plastic mass did not correlate with body weight. Total PCB (sum of 24 congeners) concentrations in the abdominal adipose tissue of 12 birds ranged from 45 to 529 ng/g-lipid. Although total PCBs or higher-chlorinated congeners, the mass of ingested plastic correlated positively with concentrations of lower-chlorinated congeners. The effects of toxic chemicals present in plastic debris on bird physiology should be investigated.