Peconic Bay Research Articles

The Annual Cycle of Zooplankton in a Long Island Estuary

Zooplankton and chlorophyll-a samples and associated hydrographic data were collected at approximately weekly intervals in the Peconic Bay estuary for most of the period between May 1978 and June 1979. Surface zooplankton samples were obtained by simultaneously-towed 73 μm- and 202 μm-mesh nets, and subsurface samples were collected with 505 μm-mesh nets. Zooplankton numbers and displacement volumes fluctuated widely throughout the year, with highest values in early spring and summer. Juvenile or adult copepods accounted for means of 90.0% and 85.0% of the animals recorded for the 202 μm- and 73 μm-net samples, respectively. The combination of Acartia tonsa and A. hudsonica adults+copepodids accounted for a mean of 81.4% of the zooplankton recorded for the 202 μm-net samples, and the combination of copepod nauplii, Acartia spp. adults+copepodids, Oithona colcarva and Parvocalanus crassirostris accounted for a mean of 82.7% of the animals recorded for the 73 μm-net samples. Copepod nauplii were the most abundant zooplankters collected in the 73 μm-net samples, and they were generally collected in higher numbers than the total number of animals in the 202 μm-net samples. During the colder months, late copepodids and adults of larger copepod species comprised greater proportions of the total zooplankton than during the warmer months when nauplii and copepodids of smaller copepod species were predominant. The ctenophore Mnemiopsis leidyi and the medusa Cyanea capillata also had periods of abundance during warmer months. Differences between numbers of larger zooplankters collected over different depth intervals or in successive replicate tows over the same depth intervals, reveal the likely effects of both vertical and horizontal patchiness. Comparisons of zooplankton numbers from the present investigation, which were obtained with relatively fine-mesh nets, with values from previous studies in adjacent waters which used coarser-mesh nets, suggest that many previous investigations have seriously underestimated the numbers of smaller zooplankters, particularly copepod nauplii.

Dynamics of phytoplankton productivity in the Peconic Bay Estuary, Long Island

Throughout most of the year chlorophyll α specific productivity (mg C/mg Chl α d −1 ) was regulated by mean photic zone light energy. During spring and early summer, however, nutrients may occasionally be important regulators of primary productivity in Little Peconic Bay, and possibly Great Peconic Bay as well. Nitrogen and silica are the nutrients implicated. Regression analysis of NO − 3 -N vs. chlorophyll α and dissolved inorganic nitrogen vs. chlorophyll α indicate that nitrogen is important in controlling the upper limit of biomass production in the ecosystem except for Flanders Bay where nitrogen appears to be in excess. Horizontal distribution of chlorophyll α is related to tidal flushing through Gardiners Bay and hypereutrophication of Flanders Bay is prevented by this physical dispersion and mixing. Annual estimates of phytoplankton productivity in the bay system range from 162 to 213 g C m −2 year −1 and are in good agreement with many other estuaries of the northwest Atlantic coast. Phytoplankton community composition, and diversity indices are discussed.

SURVIVAL AND GROWTH OF CLAM AND OYSTER LARVAE AT DIFFERENT SALINITIES

1. The optimum salinity for the development of straight-hinge larvae from eggs of clams from Long Island Sound is about 27.5 p.p.t.2. The salinity range for development of eggs of these clams is from 20.0 p.p.t., at which salinity only 16 per cent to 21 per cent of the eggs develop, to 35.0 p.p.t., at which salinity only 1 per cent or less of the eggs develops normally.3. The optimum salinity for growth of clam larvae after they reach the straight-hinge stage is 27.5 p.p.t. or higher, while 15.0 p.p.t. is the lowest salinity at which appreciable growth occurs, and 17.5 p.p.t. is the lowest at which we were successful in rearing clam larvae to metamorphosis.4. Both the optimum salinity and the salinity range for the development of straight-hinge larvae from eggs of the American oyster appear to be governed by the salinity at which the parent oysters develop gonads.5. The optimum salinity for the development of eggs of oysters from Long Island Sound, Peconic Bay, and Hodges Bar, Maryland was about 22.5 p.p.t. when these oysters developed gonads at a salinity of 26.0-27.0 p.p.t.6. When Hodges Bar oysters developed gonads at a salinity of approximately 8.74 p.p.t. the optimum salinity for the development of their eggs was between 10.0 and 15.0 p.p.t. and appeared to be dependent upon the salinity at which the parent oysters were kept immediately prior to spawning.7. The salinity range for development of normal straight-hinge larvae from eggs of these low salinity oysters was from 7.5 to 22.5 p.p.t., whereas the range for eggs from oysters conditioned at 26.0-27.0 p.p.t. was from 12.5 to above 35.0 p.p.t.8. The optimum salinity for growth of larvae of Long Island Sound oysters, conditioned and spawned at 26.0-27.0 p.p.t., was 17.5 p.p.t.9. The optimum salinity for growth of larvae of Hodges Bar oysters, conditioned and spawned at 26.0-27.0 p.p.t., appeared to be about 22.5 p.p.t.10. It is still undetermined whether the optimum salinity for growth of larvae is influenced by the salinity at which the parent oysters develop gonads.

Scientific Serials

American Journal of Science, December 1890.—Long Island Sound in the Quaternary era, with observations on the submarine Hudson River channel, by James D. Dana. The discussion of a chart containing some new soundings recently made under the direction of the U.S. Coast and Geodetic Survey leads Prof. Dana to conclude that during the Glacial period “Long Island Sound, instead of being, as it is now, an arm of the ocean twenty miles wide, was for the greater part of its length a narrow channel serving as a common trunk for the many Connecticut and some small Long Island streams, and that the southern Sound river reached the ocean through Peconic Bay. Under these circumstances the supply of fresh water for the Sound river would have been so great that salt water would have barely passed the entrance of the Sound.” He attributes the origin of the channel over the submerged Atlantic border to the flow of the Hudson River during a time of emergence.—The preservation and accumulation of cross-infertility, by John T. Gulick. The author discusses some of the conclusions arrived at by Mr. Wallace in his work on “Darwinism.”—The deformation of Iroquois Beach and birth of Lake Ontario, by J. W. Spencer. The author believes that the great Iroquois Beach was constructed approximately at sea-level and that its upheaval was the means that gave birth to Lake Ontario. This episode commenced almost synchronously with the creation of the Niagara Falls.—Experiments upon the constitution of the natural silicates, by F. W. Clarke and E. A. Schneider.—Eudialyte and eucolite, from Magnet Cove, Arkansas, by J. Francis Williams.—Prediction of cold waves from Signal Service weather maps, by T. Russell. In addition to the regular fall of temperature that takes place from day to night, irregular falls occur from time to time. When the fall in the latter case exceeds 20°, and covers an area greater than 50,000 square miles, and the temperature in any part of the area falls as low as 36°, it is called a cold wave. The author has investigated the shapes and relative positions of the various high and low areas of pressure preceding cold waves, and proposes a method for the prediction of them.—On a peculiar method of sand transportation by rivers, by James C. Graham. Numerous blotches of sand, some about six inches square, have been observed floating on the surface of the Connecticut River. This indicates that, by surface tension, it is possible for coarse sand to be floated away on a current having less velocity than would otherwise be required, and affords a possible explanation of the coarser particles of sand usually found in otherwise very fine deposits.—Note on the Cretaceous rocks of Northern California, by J. S. Diller.—Magnetic and gravity observations on the west coast of Africa and at some islands in the North and South Atlantic, by E. D. Preston.—On the Fowlerite variety of rhodonite from Franklin and Stirling, N.J., by L. V. Pirsson.—Some observations on the beryllium minerals from Mount Antero, Colorado, by S. L. Penfield.