CHAPTER 3. COMMUNITY DESCRIPTION 



Rubble-structure communities consist 

 of, and interact with, a wide variety of 

 different flora and fauna including: 

 plankton, seaweeds, invertebrates, fishes, 

 and birds. This chapter describes the 

 most apparent groups of organisms 

 associated with rubble structures and, 

 where appropriate, discusses prominent 

 species and their patterns of recruitment 

 and distribution. Feeding habits and 

 basic natural history are also treated 

 here. Detailed aspects of the ecology of 

 these organisms and communities are 

 discussed at length in the following 

 chapter on ecological patterns and 

 processes. 



3.1 PLANKTON 



Both phytopl ankton and zooplankton 

 serve as important foods for benthic 

 filter feeders and for some juvenile 

 fishes on jetties. The availability of 

 these foods may change on time scales of 

 hours, days, or seasons (Harris 1980; 

 Litaker et al . 1987). This is especially 

 true on inlet jetties, which are affected 

 by oceanic waters at high tide and by more 

 productive, estuarine waters at low tide. 

 There are also significant seasonal and 

 diel effects caused by interactions among 

 rainfall, evaporation, terrestrial runoff, 

 and diel patterns in phytoplankton growth 

 (Litaker et al . 1987). As an example, in 

 winter the estuarine waters behind the 

 Outer Banks of North Carolina are 

 dominated by riverine inputs because of 

 high rainfall and low evaporation. 

 Growth-limiting nitrogen is supplied as 

 nitrate and ammonium by runoff from the 

 drainage basin. In summer, the lower 

 rainfall and higher evaporation rates 

 cause this area to function more like a 

 lagoon. Most nitrogen is supplied as 

 ammonium due to biological regeneration. 



In winter, diel changes in phytoplankton 

 abundance are small. In summer, an 

 outgoing tide in late afternoon can have 

 twice the abundance of phytoplankton as an 

 outgoing tide in early morning (Litaker et 

 al. 1987). 



Zooplankton communities are composed 

 of permanent zooplankters (holoplankton) , 

 such as copepods, and of the larvae of 

 benthic organisms (meropl ankton) , 

 including those on rubble structures. 

 There are large fluctuations in density 

 and species composition of holoplanktonic 

 organisms. These are due to seasonal and 

 diel changes in temperature, and predation 

 by fish and other zooplankters (Fulton 

 1983, 1985). Fluctuations in the 

 abundance of larvae from the benthos could 

 be affected by the same factors but will 

 also be significantly affected by the 

 timing of larval release. 



3.2 SEAWEEDS 



Community Composition 



Most of the South Atlantic Bight is 

 an inhospitable habitat for seaweeds 

 because of the large expanses of 

 unconsolidated sands, silts, and muds to 

 which most seaweeds cannot attach. 

 Natural intertidal rocks are rare, 

 occurring at only a few places near the 

 border between North and South Carolina, 

 and at Marineland, FL. On the Continental 

 Shelf, there are outcrops of sedimentary 

 rocks that start just south of Cape 

 Hatteras and run all the way to Florida. 

 However, most of these outcrops are 

 covered by sediment and so are not 

 available for attachment by seaweeds. 

 Hard substrates that are available for 

 attachment occur most abundantly in Onslow 

 Bay, NC, and on the coast near Palm Beach, 



