Jul 21 2011

Benthic Communities

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Benthic communities can be severely altered by almost any type of construction.  Stirring up sediment makes it very difficult for filter-feeding organisms to get the nutrients they need.  Also, toxins that have settled out become re-suspended when the bottom is disturbed.  This problem has the greatest implications for the burying of transmission lines.  A 2002 study showed that 1 month after a pipeline was laid in an estuary, none of the previously existing invertebrates where present.  Even after 6 months, some species had still not returned (Lewis).  This shows us that massive disturbances of benthic communities can completely alter the local ecosystem and ruin natural diversity, possibly for many years.

http://www.tmsi.nus.edu.sg/environmental-monitoring-and-dynamics

Another problem associated with the introduction of man-made substrata is the colonization of invasive species.  When an ecosystem is upset, non-native species with no natural predators can enter the open niche and out-compete native species for resources.  Studies show that “the presence of sheltered human-made hard substrata… could enhance the dispersal of invasive species” especially in zones of eutrophication (Bulleri).

 

by Ciorra Photography

 

 

One positive bottom effect of creating an offshore wind generating facility is the potential for oyster colonization.  Oysters prefer hard substrates over sandy bottoms and are likely to grow on turbine foundations.  Oysters filter water of many contaminants and are a great asset to estuarian ecosystems.

3 responses so far




3 Responses to “Benthic Communities”

  1.   Reece Williamson 15 Jul 2014 at 3:33 am

    Undoubtedly, the construction of any type of ocean renewable energy device will have an effect on benthic communities; however, the extent of the effect and whether it can be considered an impact, positive or negative, has yet to be determined in many cases. The burying of transmission lines certainly has an effect on benthic communities. Some effects of the burying of transmission lines which need to be considered and evaluated with further research include thermal effects as well as electromagnetic effects.
    Heat loss is associated with conductivity. When electricity travels through a material, some heat is lost and given off to the surrounding environment. Some predict that the generation of electricity will result in temperature increases within a few centimeters around transmission lines (Boehlert/gill). This heat increase would also have an effect on benthic communities; however, more research is needed to discern the significance of the effect caused by the presence of transmission lines. Research nonspecific to the presence of transmission cables or oceanic renewable energy devices has indicated that increased temperatures in benthic communities leads to an elevated total biomass and a greater number of large organisms. Additionally, the increase in temperature escalates the rate of decomposition in these benthic communities (Dossena). With the presence of transmission lines carrying electricity comes the presence of an electromagnetic field. Species which utilize electromagnetic fields for prey or mate detection will likely be affected by such lines.
    A further effect associated the presence of oceanic renewable energy devices in benthic communities is the creation of additional habitats. Many devices will provide for the creation of artificial reefs which will lead to the aggregation of various species. The new habitats will stimulate some species while negatively affecting others (Langhamer and Wilhelmsson, 2009). The placement of devices in sandy seafloor locations will likely result in higher biodiversity; however, it would also result in higher predation. Moreover, the new firm-ground or hard bottom of the floor resulting from the construction and structure of ocean renewable energy devices would allow for the development of new species. Whenever a new habitat is being occupied, the opportunity for species invasion exists as well. Another effect of the presence of renewable energy devices in the ocean that should be considered is the formation of fish reserves due to the likely inactivity of boats and fishermen around areas with these devices. Consequently, seabirds would find increased feeding ability and likely congregate around these areas. Larger marine predators would also find enhanced feeding opportunity and thus aggregate around these areas as well.

  2.   Reece Williamson 15 Jul 2014 at 3:55 am

    Citations:
    U.S. Department of Energy . (2009). Report to Congress on the Potential Environmental Effects of Marine and Hydrokinetic Energy Technologies, 89.

    Wilhelmsson, D., T. Malm, and M.C. Ohman. 2006. The influence of offshore wind power on demersal fish. ICES Journal of Marine Science 63:775–784.

    Addis, P., A. Cau, E. Massuti, P. Merella,
    M. Sinopoli, and F. Andaloro. 2006. Spatial and temporal changes in the assemblage structure of fishes associated to fish aggregation devices in the Western Mediterranean. Aquatic Living Resources 19:149–160.

    Langhamer, O., D. Wilhelmsson, and J. Engstrom. 2009. Artificial reef effect and fouling impacts on offshore wave power foundations and buoys: A pilot study. Estuarine, Coastal and Shelf Science 82:426–432.

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