OS34B-01 INVITED
Long-Term Ecological Change in the Wadden Sea
The North Sea (eastern Atlantic, Europe) is among the most intensely used coastal seas. A large part of the eastern coastal region is covered by the Wadden Sea, a shallow tidal sea protected from the North Sea by barrier islands. It is characterized by a high productivity and harbors a rich sea live. It is also under strong human pressure. A large part of the continental run-off passes along the Wadden Sea. Coastal protection measures have squeezed the Wadden Sea into a narrow zone. In this presentation an overview of ecological change in the Wadden Sea will be presented. Focus will be on eutrophication, but other aspects of ecological change will be addressed. It will be shown, that after reaching a maximum during the mid 1980's riverine nutrient loads are now decreasing. As a response, coastal eutrophication is slowly decreasing. This is documented by several nutrient and chlorophyll time series in the Wadden Sea. Possibly, a recent increase in seagrass is also related to the decreased nutrient loads. In addition to eutrophication, climate change has a large impact on the long term dynamics: In the Northern Wadden Sea, warmer winters lead to a general decrease in the spring bloom and a recent decrease in mean autumn wind speed has lead to a longer phytoplankton growth season. Whereas the present de-eutrophication suggests the potential of the area to return to previous lower production levels, other changes e.g. caused by introduced species have a permanent character. Scenarios will be discussed how the Wadden Sea may respond to future coastal change.
OS34B-02
Paleoecological Perspectives on Tidal Marsh Degradation at Elkhorn Slough, California
Elkhorn Slough is the second largest area of estuarine tidal wetlands in California, and one of the first U.S. estuarine sanctuaries. Region-wide, 90% of historic tidal wetlands have been lost or restricted from tidal flow due to diking for agricultural use, salt pond construction, and development. However, wetland loss at Elkhorn Slough is currently being driven largely by tidal erosion, and the subsequent expansion of tidal channels and shoreline recession. This study reports on the use of paleoecological analyses to support and inform current restoration and conservation activities at Elkhorn Slough. Analyses of three sediment cores for fossil pollen, organic content, accretion rates, and the removal and stratigraphic description of twelve additional cores have established the timing of marsh establishment, current and prehistoric estuarine salinity, wetland plant abundance and distributions, and the relative contributions of mineral and organic sediment to wetland sediment accumulation. By understanding prehistoric processes and conditions and past variability more thoroughly, managers will be able to evaluate conservation, restoration, and management alternatives in a more informed fashion.
OS34B-03
Eutrophication Process on Coastal Lagoons of North of Sinaloa, Mexico
Coastal ecosystems in the Gulf of California support diverse and important fisheries and are reservoirs of great biological diversity. In northern Sinaloa, population growth and development, as well as increased use of these natural systems for recreation, has substantially increased the pressure placed upon marine resources. Discharge of untreated wastewaters generated by diverse human activities has been notably altered its health and integrity, principally along the lagoon's eastern shore In the late 60s, agriculture moved into a dominant role in coastal northern Sinaloa. The coastal plain encompasses more than 200,000 hectares under cultivation that now introduces large amounts of organic material, pesticides, heavy metals, and fertilizers into the lagoon systems of Topolobampo and San Ignacio-Navachiste-Macapule System at drainage discharge points and a minor grade in Colorado Lagoon. These lagoons are shallow and exhibit low water quality, lost of lagoon depth, presence of toxic substances (heavy metals) near the discharge points of wastewaters, and presence of harmful algal blooms. With the aim of evaluate the nutrients loadings (wastewaters, groundwaters) and their effects on the coastal lagoons of north of Sinaloa, the preliminary analysis of the physical, chemical and biologic variables data series are analyzed. From 1987-2007 eutrophication process is identified in Topolobampo Complex show increase tendency in annual average concentrations of DIN (Dissolved Inorganic Nitrogen= NO2+NO3) from 0.5 μ M in 1987 to 2.7 μ M in 2006. Trophic Index (TRIX) values, low nutrient ratios (N: P and N: Si) and the phytoplanktonic community structure support this result. Preliminary results of nutrients loadings show a mayor contribution of wastewaters into the coastal zone.
OS34B-04
Benthic Nutrient Fluxes in the Black Sea - Historical Legacy of Eutrophication
The broad and shallow western Black Sea shelf suffered from pollution, eutrophication and overfishing from the 1960s to the early 1990s and experienced severe changes in the ecosystem structure and functioning as a result. Eutrophication has been imposed on the western shelf largely by external point sources which are the major inflowing rivers Danube, Dniestro and Dnipro by their nutrient load. Recurrent widespread bottom water hypoxia during 20 years caused deterioration of the benthic system. After the collapse of the centrally planned industries and agriculture in the eastern European countries in the early 1990s, resulting in decreasing nutrient discharge by the rivers, the ecosystem is now responding to the decrease in anthropogenic pressures. It is not known however, how resistant the benthic and pelagic ecosystems are to further stress and what the thresholds are. Climate changes introduce further stress to the shelf ecosystems by temperature rise and by changes in the freshwater supply from the rivers. An important internal source for eutrophication, often ignored though, is recycling of nutrients from organic matter deposited on the seafloor. Benthic nutrient fluxes measured in 1995, 1997, 1998 and 2006 on the western Black Sea shelf did not decrease during that period of time despite the recovery of the pelagic system. Release of nutrients from the sediments along with a tight benthic-pelagic coupling on the shallow shelf continues to fuel benthic and pelagic productivity decades after outside pressures on the shelf ecosystem in the form of river nutrient input have decreased. This underlines the importance of the benthic system as the memory of past eutrophication. Our recent survey further indicates that from the biogeochemical point of view the state of the benthic system along the Romanian and Ukrainian Black Sea coast is nevertheless improving as bottom water hypoxia is much less prevalent and severe than a decade ago. Benthic flux experiments in a red algal field showed that a healthy benthic ecosystem with macrophytes and macrozoobenthos in balance releases less organic and inorganic nutrients to the sediment overlaying water than a disturbed system without macrobenthic life. Our experiments further indicate that a recovered benthic system with opportunistic species may fulfil ecosystem functions comparable to a pristine system. Our results will help to identify the thresholds for resilience of the benthic and pelagic ecosystems on the western Black Sea shelf. Integrating these new and existing data on sources and sinks of nutrients in the western shelf of the Black Sea into budget models may assist in developing ecological management scenarios for western Black Sea shelf.
OS34B-05
Sediment Monitoring at Vieques National Wildlife Refuge in Puerto Rico: Assessing the Current Conditions
Environmental monitoring and assessment of the current conditions of the sediment quality at the municipality of Vieques, Puerto Rico has been conducted during the past three years. Vieques underwent military practices since the creation of the US NAVY Atlantic Fleet Weapons Training Facility, resulting in the release of several contaminants, including heavy metals and depleted uranium. US Navy activities began during the 1960's and cease in 2001. Former US Navy lands were transferred to the US Fish and Wildlife Service creating the Vieques National Wildlife Refuge in 2003. This ongoing project focuses on the characterization of the sediment properties of the region. Surface and downcore sediment analysis has been conducted indicating the presence of Cs-137 in the sediments of the island of Vieques. Activity ranges from below detection limits to 0.01 Bq/g. Currently, ICP-OES analysis is being conducted to determine profiles and the likelihood of oxic, suboxic or anoxic conditions. Cs-137 retention is strongly influenced by particle grain size and clay mineralogy. X-ray diffraction analysis is being conducted to investigate adsorption and retention capacities of local sediment particles. Research findings will help guide future management practices and determine if this area serves as a sink for anthropogenic contaminants that could negatively impact the environmental quality.
OS34B-06
How Changing Human Lifestyles are Shaping Europe's Regional Seas
European society is experiencing unprecedented changes triggered by expansion of the European Union, the fall of Communism, economic growth and the onset of globalisation. Europe's regional seas, the Baltic, Black Sea, Mediterranean and North-East Atlantic (including the North Sea), provide key goods and services to the human population but have suffered from severe degradation in past decades. Their integrity as coupled social and ecological systems depends on how humanity will anticipate potential problems and deal with its ecological footprint in the future. We report the outcome of an EU-funded 15-country, 28 institution project entitled European Lifestyles and Marine Ecosystems (ELME). Our studies were designed to inform new EU policy and legislation that incorporates Ecosystem-Based Management. ELME has modelled the key relationships between economic and social drivers (D), environmental pressures (P) and changes in the state of the environment (S) in Europe's regional seas. We examined four key issues in each sea: habitat change, eutrophication, chemical pollution and fisheries. We developed conceptual models for each regional sea and employed a novel stochastic modelling technique to examine the interrelationship between key components of the conceptual models. We used the models to examine 2-3 decade projections of current trends in D, P and S and how a number of alternative development scenarios might modify these trends. These simulations demonstrate the vulnerability of Europe's seas to human pressure. As affluence increases in countries acceding to the EU, so does the demand for marine goods and services. There are ‘winners' and ‘losers' amongst marine species; the winners are often species that are opportunistic invaders or those with low economic value. In the case of eutrophication, semi-enclosed seas such as the Baltic or Black Sea are already affected by the ‘legacy of the past'; nutrients that have accumulated in soils, ground waters and sediments and are gradually released to the water column. This situation is analogous to climate change ‘locked in' by current greenhouse gas concentrations that are products of past economic activities. For the Baltic Sea for example, only a radical reduction in both phosphorus and nitrogen loads to the sea would overcome eutrophication, and future management strategies must contemplate adaptation as well as mitigation. These strategies will also need to accommodate climate change, regime shifts and emergent issues such as ‘lifestyle' chemicals and the massive development of offshore renewable energy.
OS34B-07
Satellite Images Analysis of Temporal Change (1979-2000) of the Mangrove Covertures that Surround the Mandinga Coastal Lagoon, Mexico.
Knowledge about the historical condition of the resources and the risk of natural hazards is an urgent necessity in developing countries. Satellite images analysis was applied in this study in order to evaluate coverture changes between 1979 and 2000. Mangroves cover large areas of coastal lagoon shoreline in the tropics and subtropics where they are important components in the productivity and integrity of their ecosystems. Visual and digital analysis of satellite images have been applied since the seventies when the first Land sat satellite was put in orbit. The digital analysis technique is mainly based on the reflectance or spectral response of the different objects laid on the earth surface as captured by the satellite. The results are useful for the environmental assessment of natural resources as forest and crops, and the quantification of hazards as fires, plagues, deforestation and urban expansion. This research surveys satellite images from the Mandinga Lagoon System, a coastal lagoon located to the south of the main port of Veracruz (19.1N, 96.1W), during three periods: 1989 1999 and 2000. The mangrove foliar cover was analyzed throughout the time. The reflectance signal of the mangrove that encircles the lagoon was taken as a base line for reference. The normalized difference vegetation index (NDVI) was computed in order to classify the vegetal coverage along the time. From our analysis we obtained that from 1979 to 1990 and from 1990 to 2000 areas of 122 hectares (approx. 305 acres) and 202 hectares (approx. 505 acres) were lost, respectively. The rates of mangrove trimming of 11.1 and 20.2 hectares yr-1 are high compared with other coastal lagoons of Mexico. The main causes of this deforestation are also discussed along with other factors as, the change of use of land and the fishery declination.