HYDRODYNAMICS AND INFERRED SEDIMENT DYNAMICS AT HARD-BOTTOM BENTHIC HABITATS IN THE DELAWARE BAY

In the Delaware estuary, hard-bottom environments are areas that possess high productivity, species diversity, and abundance in the otherwise muddy estuary. Hard-bottom habitat locations are limited by both sediment size and sediment dynamics, which are influenced by local hydrodynamics. We present data on local current and inferred sediment transport properties at hard-bottom sites. Intertidal beaches in Delaware Bay with relatively coarse-grained sediment are host to sandbuilder reef colonies created by Sabellaria vulgaris, while offshore slough sites contain tubeworm nodules (mixed Sabellaria vulgaris and Hydroides dianthus). Hydrodynamic conditions capable of initiating sediment suspension are critical for tube growth and maintenance, but conditions necessary to encourage the formation of different habitat structures is unknown. A bottom-mounted acoustic Doppler current profiler (ADCP) was deployed at an offshore hard-bottom site to measure local waves and currents. A co-located downward-facing high resolution pulse-coherent ADCP (PCADCP) and rotary sonar were deployed in the intertidal zone bayward and landward of a reef to measure local currents and bed geometry. Rotary sonar images reveal that the intertidal reef site is morphologically highly active. It is expected that the data will support the hypothesis that hydrodynamics are a limiting factor in the location of different forms of S. vulgaris habitat structure.