BOTTOM LIFE: 



Jntoczk Mature s^ecrets 



By Ann Green • Photographs by Scott D. Taylor 



A 



is a tiny wave ripples onto a sandy 

 marsh off the Cape Fear River, North 

 Carolina Sea Grant researcher Martin Posey 

 stands knee deep in soft mud. 



Dressed in knee-high olive boots, a 

 checkered shirt and jeans, Posey places a 

 cage on the muddy sand flat. 



The cage will keep out fish and crabs 

 and stay in place for a month, along with six 

 other cages. Some of the cages have 

 nutrients added. Others are nutrient-free. 



A short, compact researcher with 

 boundless energy, Posey relishes his hands- 

 on work in the flat, muddy marsh. "I love 

 going out in the field instead of pushing 

 paper," says Posey while digging in the 

 mud. "This is where it is actually happening. 

 It is easy to get lost in the numbers." 



Posey also wades in the shallow 

 copper-colored water and helps his 

 assistants pull in a seine net filled with small 

 predators, including flatfish, blue crabs and 

 juvenile croakers. 



The marsh's isolation — in the shallow 

 shoulder areas along the Cape Fear River — 

 provides an excellent laboratory for Posey 

 and his colleagues to study the effects of 

 nutrient loading on estuaries. 



Although there have been numerous 

 studies on the detrimental effects of nutrients in 

 fresh water, this is one of the first times 

 scientists have experimentally studied the 

 effects of nutrient loading on bottom 

 communities in North Carolina tidal creeks. 



Posey, along with colleagues and 

 graduate students, found that low levels of 

 nutrients increased the growth of benthic 

 microalgae — single-celled algae living on 

 the bottom of North Carolina's estuaries. 



However, added nutrients did not result 

 in more or larger small bottom animals, 

 including the many small invertebrates that 

 are food sources for fish and crabs. 



Algae are a major source of plant 

 production on tidal flats and form the base 

 of many food chains. Posey says the results 

 suggest that the effects of added nutrients 

 may be more complex than often thought. 



"Within several weeks, low nutrient 

 loading created a greater biomass of algae," 

 says Posey, a professor at the University of 

 North Carolina at Wilmington. "We know 

 the grazing animals sometimes can keep 

 algae under control and that increased algal 

 production can lead to increased number 

 and/or sizes of the animals that feed on them. 



"One of our questions was whether 

 increased nutrients may lead to increased 

 numbers of bottom animals — the food for 

 many fish and crabs. Surprisingly, small 

 increases in nutrients led to more algae but 

 not more fauna, making the issue of nutrient 

 additions in coastal waters much more 

 complex than we had previously thought." 



Posey says the study may have important 

 implications for the state's water quality. 



"Even though water quality is meeting 

 the Environmental Protection Agency's 

 guidelines, biology and the food web also 

 affect and are affected by water quality," he 

 says. "Our results suggest that the health of 

 the fish population may influence food-web 

 response to moderate nutrient loading. We 

 are seeing small differences in communities 

 with low to moderate nutrient loading. This 

 suggests there may be a threshold for 

 change at higher nutrient loadings." 



Multiple Studies 



Posey's estuarine study isn't the only 

 cutting-edge research that he's spearhead- 

 ing. He is involved in numerous projects — 

 from discovering new nursery areas for blue 

 crabs to the effects of experimental trawling 

 on benthic communities. 



Continued 



LEFT: Martin Posey relishes his research in the flat, muddy marshes. 



COASTWATCH 43 



