Impacts of Landbased Marine Pollution on Ecosystems in the Caribbean Sea..doc

Impacts of Land-based Marine Pollution on Ecosystems in the Caribbean Sea. Diego L. Gil-Agudelo1 and Peter G. Wells21 Instituto de Investigaciones Marinas y Costeras INVEMAR, Cerro Punta de Betín, Zona Portuaria, Santa Marta, Colombia. Tel: +57 (5) 421 1380 x 141 diego.gilinvemar.org.co2 Marine Affairs Program and International Oceans Institute, Dalhousie University, Halifax, Nova Scotia, B3H 3J5, Canada Tel: +1 (902) 237 0600 oceans2ns.sympatico.caAbstract: Land-based marine pollution (LMP-LBA) is complex, population dependent, expensive to remedy, and a threat to both human and marine ecosystem health. It is one of the most difficult marine issues to tackle and resolve successfully. Scientists, managers and policy makers have addressed it in many coastal states since the 1960s, placing pollution control into several treaties, agreements and conventions, most of them still being implemented. This paper discusses sewage (domestic and industrial), heavy metals, hydrocarbons, sediment uploads and agrochemicals as the most important sources of LMP pollution to the Caribbean Sea region. It also addresses invasive species, marine debris and thermal contamination as threats to the health of the most important coastal and offshore ecosystems of the region. The harm that pollutants cause to species and habitats e.g. coral reefs and mangrove forests, is contrasted with the potential of some marine ecosystems to resist and recover from some types of pollution e.g. oil spills. The paper serves as a guide to environmental managers on the priority LMP issues in the Caribbean Sea region, and aspects of each issue to consider with urgency and commitment. IntroductionThe Caribbean Sea is one of the worlds largest salt water seas, with approximately 2.500.000 km2 encompassing a wide variety of ecosystems including coral reefs, mangroves, seagrass beds, rocky shores, soft bottoms, and others (Sheppard, 2000). An estimated 100 million people now live in the area in 26 countries and 19 dependent territories (Fanning et al., 2007), using the Caribbean Sea as a source of goods and services and in many places highly impacting its ecosystems (Jackson, 1997).Land-based marine pollution is a well recognized coastal issue for coastal states globally and is considered, due to its inherent complexity from sources to governance, to be one of the most difficult marine environmental issues to tackle and resolve successfully. Scientists and managers alike have been addressing the issue in many countries since the 1960s. Marine pollution was defined early on by the United Nations GESAMP, in an internationally accepted definition, as being “ the introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to maritime activities including fishing, impairment of quality for use of sea water and reduction of amenities.” (GESAMP 2001). Pollution from the land was given special attention in the 1980s, through recognition in Section XII of UNCLOS (1982); at the UNCED “Rio” Conference, with Agenda 21 (1992); at the various intergovernmental meetings producing the Montreal Guidelines (1985) and the Washington Protocol (1995); and with an emphasis on the problem in GESAMPs state of the marine environment reports (GESAMP 1990, 2001a,b). Article 207 of the UNCLOS (1982) states that “States shall adopt laws and regulations to prevent, reduce and control pollution of the marine environment from land-based sources, including rivers, estuaries, pipelines and outfall structures, taking into account internationally agreed rules, standards and recommended practices and procedures. ” This set the stage for further international discussion of how to address the issue comprehensively, without setting up a new legally binding Convention or Agreement. The UN led Washington Protocol Conference of November, 1995, was particularly important as the problem was exhaustively described, an international framework of priorities was prepared, and the Global Program of Action, with national programs of action, was initiated with the intention to report on progress every five years. Whether this approach will be effective at reducing pollution impacts remains to be seen (VanderZwaag et al., 1998), but to date, parties have met regularly to report on activities, despite the increasing challenges.Sewage and municipal effluents are still on top of the list of the wide range of land-based marine pollutants. Sewage control is a problem considered almost intractable in many countries, given the size of their coastal populations and cities, the volumes and complex composition of the effluents, and the costs of effective treatment and the maintenance of the sewage treatment plants (STPs). While coastal sewage treatment is considered a high priority in the United States, with very large investments being made (e.g. the Deer Island STP in Boston at 4.1 Billion US $), other advanced countries such as Canada and the UK are still building STPs to treat discharges to the sea and only at basic levels of treatment. For example, Halifax, NS, is just putting in three more STPs for advanced primary treatment and still has combined sewer and overflow systems, hence major rain events which are common move raw sewage of 200-300,000 people into the sea as before. Surprisingly, some very wealthy island states such as Bermuda in the Sargasso Sea pump their screened raw sewage directly into the ocean, despite affecting water and amenity beach quality close to the discharge points (Bermuda Biological Station, unpubl. data). Advanced secondary treatment is considered minimal for the protection of human and ecosystem health (Dan Smith, Univ. Alberta, pers. comm.) and the UN-WHO. The costs of discharging untreated sewage into coastal ecosystems are very high, both in terms of closed fisheries (especially shellfisheries) and risks of disease to humans (GESAMP 2001a,b), countering the initial high costs of building STPs and the costs of long-term maintenance. Chemical contaminants from the land, if persistent, bioaccumulative and toxic at low levels (i.e. having the properties of the formally recognized POPs or persistent organic pollutants), can cause many problems in coastal regions. Many constituents are endocrine disrupters, affecting growth and development. Nutrients such as nitrogen contribute to oxygen deficits, eutrophication, and harmful algal blooms. Sediments become contaminated and acts as sinks and sources of chemicals for many years. The extent of impacts depends upon properties of the chemicals, volumes, flushing rates, and characteristics of the organisms and ecosystems being exposed. Some organisms take up many contaminants, from metals to pesticides to PAHs, but are relatively resistant to effects e.g. clams, mussels. Others are highly sensitive to water quality changes and low levels of organics e.g. many marine larvae, decapods, echinoderms. Many of the organisms found in coral reef and mangrove ecosystems are sensitive to pollutants at very low levels, especially during reproduction and development. Ecosystems can recover from some chemical exposures, such as from petroleum oil spills, again if oceanic conditions lead to diminished exposures, degradation of the chemicals, and high recruitment from adjacent non-impacted areas. In the long term, constant elevated sediment loadings to coral reef ecosystems may have a greater impact on overall reef health than chemical exposures.Many inshore areas around the Caribbean countries are degraded for water and sediment quality; this situation will only become worse if not directly addressed (Bryant et al., 1998; Burke and Maidens, 2004). Cumulative changes to many habitats have taken place along many coastlines. Unfortunately, not enough is known comprehensively about the ecotoxicology of tropical and sub-tropical ecosystems, including their resilience and recovery rates, to permit more refined comment on the persistence of land based pollution impacts, and the recovery potential, in the Caribbean. On the positive side, this question is being addressed by programs such as the Large Marine Ecosystem (LME) (K. Shermans many LME publications) and by professional organizations such as SETAC (Society for Environmental Toxicology and Chemistry), Latin America section, hopefully fast enough to make a difference to the quality of Caribbean coastal and offshore waters. Article 7 of the Cartagena Convention, which was subscribed in 1983 stipulates that “The Contracting Parties shall take all appropriate measures to prevent, reduce and control pollution of the Convention area caused by coastal disposal or by discharges emanating from rivers, estuaries, coastal establishments, outfall structures, or any other sources on their territories.” To date, the Protocol on Marine Pollution from Land-based Sources and Activities (LBS Protocol) has been signed by only six countries (Colombia, Costa Rica, Dominican Republic, France, Netherlands and the United States of America), and ratified by only three (Trinidad and Tobago, Panama and France); other countries are analyzing and evaluating their ratification to the protocol (http:/www.cep.unep.org, accessed Oct. 28, 2008, INVEMAR et al., 2004b). As a consequence, at this time, this protocol is still far from being effective as its implementation remains to be done by most countries in the Caribbean.Major Marine Pollutants in the Continental Caribbean Region and Their Effects on Marine EcosystemsThroughout the years, authors have classified land-based pollutants in different categories (see GESAMP, 1990, 2001a,b; UNEP, 1999; Islan and Tanaka, 2004). For the purpose of this paper, and to assist focusing on their ecological consequences and management, we are considering the major pollutants as below.Sewage (domestic and industrial)Domestic and industrial sewage, i.e. municipal effluents, constitutes the largest volume of waste discharges to marine ecosystems (Islam and Tanaka, 2004). These pollutants are discharged mainly by cities as domestic and industrial wastes, but also are discharged by aquaculture facilities and other types of developments (Loya et al., 2004), including discharges from ships legally permissible under the MARPOL 73/77 Convention.Sewage contains a wide variety of pollutants at highly variable concentrations and volumes. These include nutrients that are probably the most noxious wastes at national and regional levels (GESAMP, 2001), to organic substances, heavy metals (see below), endocrine disrupting chemicals (i.e. estrogens, Atkinson et al., 2003) and microbes (including pathogens) (Harvell et al., 1999; Sutherland and Ritchie, 2004). Other growing industries in the Caribbean region, such as aquaculture, exacerbate the problem by discharging their wastes directly into the ocean and nearby ecosystems. Such discharges contain not only organic matter and nitrogenous compounds produced by the metabolism of organisms, but also contain dissolved and suspended solids, large amounts of antibiotics used in intensive farming (Gautier, 2002), pathogens, and other compounds and agents harmful for marine life (GESAMP, 2008). The chemical constituents of sewage affect aquatic organisms in many different ways, as they range from trace metals to complex organics such as PAHs, pesticides, surfactants, and drugs and their metabolites, with many different scenarios of uptake and toxic action. Effects include sub-cellular responses, direct toxicity or poisoning, disruption of reproductive behavior, changes in reproductive development e.g. feminization of male fish, and other lethal and sublethal effects, some of them difficult to evaluate, especially under field conditions. Effects are only understood for a relatively small number of species, although there is some capacity for inter-species comparisons and extrapolations. These responses are initiated largely at the molecular and cellular levels of biological organization (Elliott et al., 2003). At the ecosystem level, sewage pollution can promote bacterial and plant growth; cause declines of oxygen levels in the water column (Islam and Tanaka, 2004), contributing to the so-called dead zones that are proliferating in coastal waters; create changes in the productivity of ecosystems, species distribution and diversity, altering size distributions of populations; and increase disease prevalence in fish and invertebrates, a notable problem near urbanized coastlines, among others (Elliott et al., 2003; Bruno et al., 2003). Under low and moderate nutrient increases from sewage, productivity increases with little change in biomass or trophic structure of the ecosystems. When these levels increase, algae usually take control of the ecosystems, causing shifts in species dominance (Pastorok and Bilyard, 1985). In Caribbean coral reefs, for example, such changes might cause coral stress by reducing light penetration, but they also promote the growth of filter feeders (e.g. sponges) that compete for space with corals. Nutrients such as nitrates at high concentrations and toxic substances (PCBs, chlorine, hydrocarbons, etc.) usually found in sewage waters can also be toxic for corals and other marine organisms (Pastorok and Bilyard, 1985; Loya et al., 2004). Sewage water and its residues may also affect the cellular defense mechanisms of organisms (Cheng, 1988) and, together with the introduction of pathogens, increase disease in coastal and marine ecosystems.It is estimated that less than 20% of sewage is treated in Latin-America and the Caribbean Sea region (Idelovitch and Ringskog, 1997; UNEP, 2003), with most of it flowing untreated to rivers and the oceans (Martinelly et al., 2006; PNUMA, 2007). As well, aquaculture facilities dump most of their residues into mangroves, expecting them to act as biofilters (Gautier, 2002; GESAMP, 2008). Heavy MetalsFernandez et al. (2007) reviewed the literature of several contaminants in the Caribbean, with special emphasis on heavy metals (Hg, Al, Cr, Cu, Fe, Mn, Cd, Pb and Zn) and organotins. Typically, tributyl tin (TBT) and heavy metals are found near cities, ports and industrial developments across the region. Traces of some of these contaminants have been found in remote areas across the region, with unknown impacts in these ecosystems. Olivero-Verbel et al. (2008), amongst others, have shown how contaminants such as Hg can move through and accumulate in food chains, including humans, even after more than 30 years of the closure of a source of contamination. Accumulation of metals and other compounds in organisms depends on factors such as their specific properties, exposure levels, routes of uptake, and sequestration