Seasonal variations in plankton trophic structure under highly eutrophic conditions

The plankton trophic structure of a hypereutrophic tropical estuarine system was evaluated in the dry and wet seasons, as well as during the dry–wet transition period, over 1 year. Correlations between micro- and mesozooplankton abundance and composition and both size-fractioned phytoplankton biomass and abiotic variables were investigated in order to understand seasonal variations in plankton interactions and provide a conceptual trophic model for the plankton community. Rainfall is the main environmental forcing factor for this system, and the plankton community responded accordingly, with different structures during each season sampled. The resulting trophic model shows a multivorous food web, where both longer microbial and shorter herbivore food webs occur simultaneously. Microzooplankton play a crucial role in this ecosystem, linking both small and large phytoplankton to the mesozooplankton. These results have important implications for estuarine management practices, particularly under highly eutrophic conditions.

Who Benefits from National Estuaries? Applying the FEGS Classification System to Identify Ecosystem Services and their Beneficiaries

In spite of their perceived value, the widespread implementation of ecosystem services assessments has been limited because of perceptions of being too technical, too expensive, or requiring special expertise. For example, federal estuary management programs have widely used ecosystem services concepts to frame management issues and communicate with stakeholders. Yet, indicators assessed, monitored, and reported in estuarine management still have traditionally focused on ecological conditions, with weak connections, if any, to social or economic outcomes. Approaches are needed which expand the range of ecosystem services that can be considered, link ecosystem services explicitly to different stakeholder groups, facilitate effective communication with economists and other social scientists, and expand the array of available valuation techniques. We applied the concept of final ecosystem goods and services to review the broad suite of ecosystem services and their beneficiaries relevant to the management of two federal programs for estuary management, the National Estuary Program (NEP) and the National Estuarine Research Reserve System (NERRS). The Final Ecosystem Goods and Services Classification System provided a structured framework for connecting ecosystem services to their beneficiaries and the environments providing them. Document analysis of management plans assessed the degree to which these programs consider ecosystem services, their beneficiaries, and habitats within the estuarine watershed. The hierarchical list of final ecosystem goods and services generated from document analysis serves as a tool for defining management goals, identifying stakeholders, developing meaningful indicators, and conducting valuation studies in estuarine management planning efforts. Though developed here for estuarine management, the keyword hierarchy and final ecosystem goods and services approach have broad applicability and transferability to other environmental management scenarios.

Modelling the Main Hydrodynamic Patterns in Shallow Water Estuaries: The Minho Case Study

Numerical models are key tools to characterize hydrodynamical patterns of coastal environments and anticipate the potential effects of hazardous and extreme events, anthropogenic intervention or climate change. In this work, the openTELEMAC-MASCARET modelling system was selected to represent the dynamics of the Minho estuary, a very shallow estuary located at the Northwestern Iberian Peninsula coast. Calibration and validation results confirm the accuracy of the numerical tool, with small root mean square errors, close to null bias and the close to unit correlation and skill coefficients obtained for water level and currents velocity at several estuarine locations. The obtained results depict a tide dominated estuary with a delay in the tide phase and a marked asymmetry in the tide curve that increases upriver. Additionally, an upstream diminution of M2 and an upstream augmentation of M4 was observed, classifying this estuary as flood-dominated. The represented current patterns show that variations in the intensities of the main driving forces alter the behaviour of the hydrodynamical patterns within the estuary, with a clear dependence on bathymetric and topographic characteristics. During flood events, larger estuarine regions become submerged due to the low margins and the wetland characteristics, highlighting the need for accurate numerical models that can be used as a decision-making support tool for effective and integrated estuarine management.

ESTUARINE MANAGEMENT AREAS: A PRIORITY RANKING SYSTEM

The Queensland Fisheries Service is the instrumentality responsible for administration of fisheries matters within Queensland, Australia. The Fisheries Act provides legislation to protect, conserve, manage and develop the aquatic resources of the State. As a means of evaluating resource data a priority ranking system is proposed which provides for both quantitative and qualitative assessments of estuaries in terms of regional planning for best land use.

COMPARISONS OF ESTUARINE MANAGEMENT NEEDS OF A TROPICAL PACIFIC MEXICAN HARBOUR AND A TEMPERATE CALIFORNIA HARBOUR

Two areas of the eastern Pacific are compared, the southern California wetlands south of Point Conception and Mazatlan, Mexico. The historical development of both areas is important in considering their present biological status. Southern California has been subjected to intensive population growth and urbanization while Mazatlan has remained relatively unchanged. Both areas are compared biologically in regards to the fish population, thermal gradients in the harbors, salinity, nitrate, nitrite and phosphate distributions. The economic importance of the harbors is recognized, however it is essential that measures are taken to restore or retain existing wetlands that are associated with the harbors. The harbors can serve as shelters for various organisms if water quality can either be maintained (as in the case of Mazatlan) or improved, and if input of toxic and excessive nutrients is limited.