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Direct underwater observations at seamounts across the western North Atlantic basin revealed the presence of the false boarfish, Neocyttus helgae (Oreosomatidae), at depths of 915 to 1829 m. These observations extend the known range of this species across the North Atlantic basin and support the hypothesis that seamounts are stepping stones for dispersal. Fishes were associated with basalt habitats featuring corals and sponges (both nearly horizontal basalt sheets and steep cliffs) as well as depressions in sheets of basalt. These features provided refuge from flow and predators as well as immediate access to zooplankton and pelagic prey delivered by rapid currents. Encounters with fishes were primarily as single individuals or pairs. Territorial behaviors, such as raised dorsal spine and lateral display, occurred when submersible vehicles approached fish, suggesting that territorial defense is a common behavioral attribute.

High resolution imaging of the seafloor has been limited to fixed sensors and/or limited field-of-view instruments. As a result, our ability to characterize large areas of benthic habitat has relied on acoustic maps and photomosaics combined with point sampling. In addition, the response of motile epibenthos and demersal fish to habitat patches, structure and disturbance has been largely inferred or based on disruptive sampling and manipulative experiments. Direct quantitative observation of large areal variation in these factors is possible through a combination of traditional video census techniques with high resolution optical imaging of the seafloor. Laser Line Scan Systems (LLSS) are capable of imaging continuous swaths of the seafloor from 3 to 15 m wide at speeds up to 5 km/h. Image quality is dependent on system performance and turbidity but can exceed limits required to distinguish benthic habitats and census undisturbed fish and epibenthos. This areal coverage rate (1 km/day) is several orders of magnitude higher than video sleds and can complement high resolution acoustic surveys (multibeam or side scan). We present results from several applications of these systems for assessment of benthic resources and disturbance in turbid estuarine environments.

Megafaunal assemblages were studied in August–September 1992 using a towed camera sled along seven cross-isobath transects on the continental slope off Cape Hatteras. A total of 20,722 megafaunal organisms were observed on 10,918 m 2 of the sea floor between the depths of 157 and 1 924 m. These data were compared with data previously collected off Cape Hatteras in 1985 and at other locations along the eastern U.S. coast between 1981 and 1987. Megafaunal populations on the upper and lower slopes off Cape Hatteras were fouond to be similar, in terms of density and species composition, to those observed at the other locations. In contrast, megafaunal abundances were found to be elevated (0.88 and 2.65 individuals per m 2 during 1985 and 1992, respectively) on the middle slope off Cape Hatteras when compared to most other slope locations ( 2 ). These elevated abundances mainly reflect dense populations of three demersal fish, two eel pouts ( Lysenchelys verrilli and Lycodes atlanticus ) and the witch flounder Glyptocephalus cynoglossus , and a large anemone ( Actinauge verrilli ). These four species dominated the megafauna off Cape Hatteras, whereas they represented only a minor component of megafaunal populations found at other slope locations. Additionally, numerous tubes of the foraminiferan Bathysiphon filiformis were observed off Cape Hatteras, but not elsewhere. The high density of demersal fish found off Cape Hatteras appears to be related to the high densities of infaunal prey reported from this area. The high densities of A. verrilli and B. fuliformis may be related to the same factors responsible for the high infaunal densities, namely enhanced nutrient inputs in the form of fine particles. Extreme patchiness also was observed in the distributions of the middle slope taxa off Cape Hatteras. This patchiness may reflect the habitat heterogeneity of this exceptionally rugged slope and the sedentary nature of the organisms inhabiting it.

The δ13C and δ15N of the soft tissues of two Calyptogena phaseoliformis specimens sampled from the floor of Ascension Fan-Valley, off the Monterey Peninsula, California, ranged from -35.0 to -33.6% and -6.2 to -0.6%, respectively. The carbon isotope abundances are similar to those of other Calyptogena known or believed to be nutritionally dependent on sulfide-based chemoautotrophic symbionts. Calyptogena δ15N values and their geographic variation indicate an unusual source of dietary nitrogen for these animals. The δ13C and δ18O values for Calyptogena shells from the Ascension and Monterey Fan-Valleys approximate those reported for Calyptogena from three other locations in the Pacific and appear to reflect shell formation from constituents within ambient deep-ocean water.

Alvin dives and camera tows within the “meander area” of the Monterey and Ascension Fan Valleys have located nine chemosynthetic communities over depths ranging from 3000 to 3600 m over a distance of 55 km. Most of the observed communities consist largely of Calyptogena phaseoliformis, but Solemya (species unknown) and a pogonophoran (genus Polybrachia), have also been identified. The δ13C values (-35.0 to -33.6 per mil) and the presence of APS reductase and ATP sulfurylase in the C. phaseoliformis tissue is consistent with sulfur chemoautotrophy. Two reduced organic matter sources for the H2S are proposed: (1) older beds exposed by the deep erosion (up to 400 m) of the fan valleys and (2) concentrations of anaerobically decomposd organic matter buried in the valley floor.

If one is concerned with the mechanisms of adaptation to environmental disturbances on the non-genetic level, hydra are particularly appropriate for several reasons. First, the problem is somewhat simplified since the behavioral repertoire of hydra is severely limited, the morphology at least on a gross and light microscopy level is reasonably simple and a spectrum of responses ranging from the cellular to the behavioral can be recorded on genetically identical individuals. As a consequence of this simplicity it ought to be possible to catalogue the response of hydra to change in such a way that we can distinguish between the rapid and slower responses and get some sense of what the implications of each of these responses might be for the further adaptive capacities of the hydra themselves. The rationale for this type of inquiry is presented in Slobodkin and Rapoport (1974 and papers cited therein.