Science Serving Maryland's Coasts
Roberta Marinelli, Ph.D.
Chesapeake Biological Laboratory
The Effect of Increased Porewater Ammonium Concentrations on Infaunal Recruitment in Shallow Water
Benthic organisms respond to chemical and physical cues that prompt them to settle or deter them from settling at a particular sedimentary site. Disturbance to the sediment from deposit-feeding, burrowing, human activity, or numerous other sources releases sulfides and ammonium from the lower sediment layers. Since these chemicals are often toxic to benthic animals, they can act as negative chemical cues for settling larvae or mobile meiofauna. In this experiment, ambient porewater ammonium concentrations in Tom's Cove in Chincoteague Bay, VA were manipulated through the burial of acrylatnide gels containing Ammonium sulfate in the muddy sediment in an intertidal zone. Porewater and sediment samples were taken above the gels four days later and analyzed for ammonium concentration and animal content, respectively. It was found that the porewater ammonium concentrations were successfully increased above the high ammonium gels, with significant difference from the control gels. There was also a significant difference in meiofaunal abundance above those two types of gels. Only nematodes and polychaetes were found in the samples. The results indicate that acrylatnide gels are useful for chemical manipulation in the field. They also reaffirm previous findings that ammonium is a negative chemical cue for settling meiofauna.
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