Showing papers by "Megan N. Dethier published in 2006"

Taxonomic sufficiency in distinguishing natural spatial patterns on an estuarine shoreline

Abstract: Studies of marine benthic communities have shown that pollution impacts can often be detected without identifying taxa to the species level, thus saving considerable time and cost. We tested whether differences among unpolluted intertidal communities along weak estuarine physical gradients could similarly be detected with various species aggregates. We used a spatially hierarchi- cal sampling design to study species-rich, low-shore communities from pebble-sand beaches in Puget Sound, Washington. Previous research showed that weak north-south gradients in salinity, wave energy, and proportion of fine sediments correlate clearly with species richness of the benthic epibiota and macroinfauna. In this study, we found similar correlations with data aggregated to the family level but weaker correlations at higher levels (class, phylum, or trophic groupings). Multivari- ate analyses of community data at the species level show distinct separation among geographically distinct areas; similar spatial patterns are visible almost as clearly when data are gathered at lower resolution in the field or when species-level data are aggregated to families. Higher-level aggrega- tions cause spatial patterns to become progressively less distinct. Much of this effectiveness of family- level aggregation stems from the biota being family-rich but with few species per family. For this biota, monitoring programs using only families or other readily identifiable taxa should be able to detect many potential changes in community patterns in space or time. Incorporating occasional sur- veys using identification and analysis at the species level would add the capacity to examine biodi- versity and possible within-family changes in species abundances.

Monitoring Rocky Shores

Abstract: Monitoring changes in the intertidal zone of rocky shores has never been more critical. This sensitive habitat at the interface of land and ocean may well be the marine equivalent of the canary in a coal mine as we advance into an era of global climate change. This handbook describes effective methods and procedures for monitoring the ecological and environmental status of these areas. Written by three collaborating authors with extensive field experience, it provides critical discussions and evaluation of the various sampling techniques and field procedures for studies of intertidal macroinvertebrates, seaweeds, and seagrasses. Rather than prescribing standard protocols or procedures, the authors break down the decision-making process into various elements so investigators can become aware of the advantages and disadvantages of choosing a particular method or approach. Chapters discuss topics such as site selection, field sampling layouts and designs, selection of sampling units, nondestructive and destructive methods of quantifying abundance, and methods for measuring age, growth rates, size, structure, and reproductive condition.

Community modification by a grass invader has differing impacts for marine habitats

Abstract: There is increasing recognition of invasive species impacts but less is known about how modifications may differ under variable environmental contexts. In particular, it is generally unknown whether impacts of single invasive species can vary among habitats and what the consequences of this variability may be. We used a multi-site comparative approach to examine the impacts of a single invader, the marine grass Spartina anglica, on estuarine habitats with different native species assemblages and physical conditions. We found that range (extent), abundance, and effects on sediment and native plant species vary depending on the habitat invaded. S. anglica has by far the greatest range and abundance in mudflats and low salinity marshes compared to high salinity marshes and cobble beaches. Changes in sediment characteristics also substantially differed among habitats, with invaded areas in some habitats experiencing greater sediment accretion, water content, and salinity than other habitats. In addition, in opposition to the theory that strong invaders decrease species diversity, we found that native plant diversity in our plots increased within invaded areas in some habitats while it declined in others. These variable modifications suggest that single invaders, even species that are considered strong interactors, do not produce the same effect in all habitats. We suggest that understanding impact variability can help predict how invasive species will respond to environmental changes, new habitats, and management strategies.

Invertebrate community responses to recreational clam digging

Abstract: Marine reserves can help in maintaining biodiversity and potentially be useful as a fishery management tool by removing human-mediated impacts. Intertidal, soft-sediment habitats can often support robust recreational and commercial shellfish harvests, especially for clams; however, there is limited research on the effects of reserves in these habitats. In San Juan County, Washington, several reserves prohibit recreational clam digging. We examined the effects of these reserves on infaunal community composition through comparison with non-reserve beaches during a 6-week period. Clam abundance, overall species richness and total polychaete family richness were greater on reserve beaches compared to non-reserve beaches. Additionally, an experiment within a reserve demonstrated negative impacts of digging on non-target infauna. These effects probably resulted from local disruption and disturbance of the sediment habitat and not from increased post-digging predation, which was controlled. Intertidal reserves could play an important role in sustaining local and potentially regional biodiversity.

Coastal Habitats in Puget Sound: A Research Plan in Support of the Puget Sound Nearshore Partnership

Abstract: : This research plan identifies high-priority research goals and objectives and delineates the critical questions and information gaps that need to be addressed to effectively undertake restoration planning and adaptive management of the nearshore ecosystems of Puget Sound To support this science-based approach and guide scientific research in support of nearshore ecosystem restoration, the US Geological Survey and the PSNERP Nearshore Science Team collaborated in development of this research plan, organized around six high-priority goals

Conceptual Model for Assessing Restoration of Puget Sound Nearshore Ecosystems

Abstract: : The PSNERP Nearshore Science Team has developed a Conceptual Model framework to aid in assessing restoration and preservation measures for nearshore ecosystems in Puget Sound. This model was designed primarily as a synthesis tool to better understand nearshore ecosystem processes and the response of nearshore ecosystems to different stressors or, alternatively, restoration actions. We have designed this model as a framework from which additional, more explicit `submodels' can be consistently developed that relate to specific nearshore stressors, landscape segments, functions, or restoration designs.

Native Shellfish in Nearshore Ecosystems of Puget Sound

Abstract: : This document describes invertebrates found in Puget sound Life history strategies, habitat requirements and anthropogenic influences are examined Stock status and population trends of commercially important species is outlined Land use and its impacts on the nearshore environment is discussed