Jeannie Gilbert

Marine and Estuarine Science Program
Department of Biology

MSc. completed July 2005

BSc Biology, Western Washington University, 2001.

    E-mail:     Jeannie.Gilbert@wwu.edu
    Phone:     360-650-7482
    Office:     BI 254
    Mail:        Biology Dept., MS 9160, WWU 
                    516 High St. 
                    Bellingham, WA 98225-9081

Project

Title: A seasonal study of the benthic invertebrate communities of the Samish River estuary.
    
Abstract: Seasonal differences in the environment are accentuated in the Samish River estuary in Washington state where the freshwater flow is extremely variable, ranging from less than 5 m3 s-1 to over 65 m3 s-1 during this study (March 2002-March 2003).  Twenty seven species were collected during the study at five stations spanning the region of greatest salinity change.   Differences in community structure were significant both between stations and seasons.  ANOSIM results revealed that 65% of comparisons between stations were distinctly different, and adjacent stations most frequently overlapped in similarity.  The top six organisms contributing to similarity within stations were Hobsonia florida, Oligochaete sp., Chironomid sp., Corophium spinicorne, Nereis limnicola, and Manayunkia aestuarina.  Biodiversity measures (Shannon-Wiener Diversity index, Margalef’s Richness, and Pielou’s evenness) were significantly different between stations and seasons with the exception of Pielou’s evenness which was not significant between seasons.  Interstitial salinity and percent organic content were also significantly different between stations and seasons.  The seasonal comparison of the benthic communities to interstitial salinity and percent organic content indicated that salinity and a combined salinity and organic effect were the strongest influence in spring and summer.  In the fall, percent organic content and the combined salinity/organic factor were strongest.  In winter no factors were significant.  Given the seasonal community variability observed during this study, a single season sample may not adequately represent the community dynamics of a small estuary.