Distribution of the cladoceran Podon polyphemoides in the Chesapeake Bay

The distribution of the cladoceran Podon polyphemoides (Leuckart) in the Chesapeake Bay (USA) estuarine system was determined by a quantitative pump sampling method, and the patterns of abundance were correlated with temperature and salinity distributions. The species was seasonally recurrent, with distinct population maxima in the central portion of the bay. Population densities in excess of 60,000 podonids/m³ have been recorded. The podonids first appeared in the spring in the shallow tributaries, when water temperatures near the bottom reached 6°C. The vernal populations disappeared when summer temperatures exceeded 27°C, but reappeared in the fall as the water cooled. The species was euryhaline and eurythermal in its distribution, but the greatest concentrations were attained within relatively narrow zones of temperatures between 11^o and 26°C, and salinities between 8 and 18. The production of males, sexual females and sexual eggs occurred both in the spring and the fall between the thermal limits of 11^o and 17°C.     

Benthic Foraminifera: morphology and growth in clone cultures of Heterostegina depressa

A three months old clone of 76 asexually produced F₂ Heterostegina depressa D'Obbigny, 1826 (Foraminifera) was subdivided into two groups which were cultivated for 5 months, one at 300 lux, the other at 600 lux. Nourishment was provided by symbiotic photosynthesizing algae. The 300-lux group added 1 whorl, the 600-lux group added 1/2 a whorl during the experiment, suggesting that the first group was nearer the optimum for growth than the second. Growth rates reacted but slowly to changes in environmental conditions. Also, specimens within the same culture dish showed great differences in response. In the 600-lux group, many specimens ceased to grow entirely, while others continued. Cessation of growth tends to produce a rounded test shape, by filling-in of the apertural angle, while rapid growth tends to be correlated with flaring tests (i.e., tests with an open spiral). In addition, there is a trend toward increased flaring during normal ontogenetic development. Shell damage is greater in rapidly growing individuals; walls are apparently thicker in slowly growing and in resting individuals. Ecological interpretation of morphological characteristics is hampered by: (1) a lag effect between growth response and environmental change; (2) slowing or termination of growth under stressful conditions with corresponding minor changes in morphology; (3) great variation in response between sibling individuals within the same culture dish; (4) aging effects.     

Dispersion of gastrotricha in a marine beach of the San Juan Archipelago,Washington

Gastrotricha were quantitatively sampled at low tide on several dates from two transeets at Eagle Cove, San Juan Island, Washington, USA, during the summers of 1963/1964. They showed low species diversity and very high whole-beach densities. Chaetonotus testiculophorus Hummon, 1966 and Turbanella cornuta Remane, 1925 were found abundantly, Paraturbanella intermedia Wieser, 1957 only rarely. Abundant C. testiculophorus were found above 100 cm elevation; T. cornuta occurred abundantly in a rip-channel trough and in the lower beach area. T. cornuta, but not C. testiculophorus, showed significantly greater clumping at high than at low density. Curves of LC₉₀ temperature-salinity tolerance for both species show that they tolerate widely fluctuating temperatures and salinities. Causes of whole-beach distribution patterns are discussed.Research was supported by an NSF College-University Association Grant (G-17537), administered by the Graduate School, University of Washington, Seattle, and was conducted at the Friday Harbor Laboratories, San Juan Island, Washington, during the summers of 1963 and 1964.     

Some observations on the influence of salinity on growth and photosynthesis inPorphyra umbilicalis

Notwithstanding the great importance of the salinity factor in the marine environment, the knowledge of influence of salinity on growth of marine benthic algae is very limited. Rate of growth (mg, cm²) and O₂ output of the intertidal red algaPorphyra umbilicalis from Helgoland, North Sea, were measured during a 3 week culture in 3 different salinities (1/2-, 1- and 2-concentrated artificial sea water; Table 1). Under hypertonic conditions (2-concentrated sea water) growth rate and photosynthesis rate were depressed, compared to values obtained in normal concentrated sea water. Under hypotonic conditions (1/2-concentrated sea water), growth expressed in mg was the same as in normal concentrated sea water, or higher when expressed in cm³. Rate of O₂ output was almost unaltered in one of the two experiments, lowered in the other. Cell size increased at higher salinity, while swelling of cell walls and intercellular substances as well as the intensity of colouring decreased with salinity. The discrepancies between growth and photosynthesis under hypotonic conditions cannot be completely explained by the observed influences of salinity on morphological structures (cell size, swelling of cell substances). Detailed studies on the time course of photosynthesis and respiration rates, and preparation of a metabolic balance for the algae are necessary.     

A rapid kinetic technique for quantifying polycarbonate species in coalspoils

A rapid, automated procedure has been used for differentiation and quantitative determination of siderite, calcite and dolomite, based on the different rates of dissolution of the three carbonate species when reacted with excess 5 mol/litre HCl. The method employs manometric measurements of acid-liberated CO₂ with a membrane differential-pressure transducer coupled to a stripchart recorder. Tested on the three carbonate species, singly and in pairs, the technique is discriminatory, sensitive and relatively rapid.Contributions from the Department of Agronomy, University of Kentucky Agricultural Experiment Station in Lexington, and Institute for Mining and Minerals Research of the University of Kentucky. The investigation reported in this paper (No. 83-3-206) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

Assimilation,inter-organ transfer and excretion of americium in two teleost fish

Radiotracer experiments were performed (February–April, 1982) to study the assimilation and metabolism of the transuranium nuclide americium-241 in the marine teleosts Serranus scriba (Linnaeus, 1758) and Scorpaena notata Rafinesque, 1810, caught off the Monaco coast. Fish fed with ²⁴¹Am-labelled food showed that assimilation of this radionuclide takes place through the gastrointestinal walls and that the small fraction accumulated is incorporated mainly in the skin, muscle and skeleton. Gut-transfer coefficients were similar in both species and averaged 0.7% (range 0.1 to 1.7%) of the ingested activity. The calculated biological half-lives for loss of the absorbed fraction ranged between 49 and 61 d for Serranus scriba and 12 and 117 d for Scorpaena notata. Results from an intramuscular injection experiment indicated that ²⁴¹Am was retained mainly in the liver, skin and skeleton; the fraction accumulated by muscle was very low. Liver displayed a relatively short biological half-time for ²⁴¹Am loss of roughly 24 d. Routes of ²⁴¹Am excretion from the teleosts appear to be through the kidneys, gills and feces with bile serving as a possible excretion route from the liver. From the limited amount of published information available for comparison, experimental evidence is presented which suggests that ²⁴¹Am taken up via the food chain is more biologically available to marine fish than is plutonium.     

Population differences in how black-tailed prairie dogs deal with snakes

Summary This paper examines the antisnake behavior of a snake-experienced Texas (TX) population and a snake-naive South Dakota (SD) population of black-tailed prairie dogs (Cynomys ludovicianus). Animals in both populations were presented with tethered rattlesnakes and nonvenomous bullsnakes before and after the first emergence of pups from their natal burrows. SD and TX adults were more likely to actively harass snakes than were pups. There were no differences in the behavior of SD adult males vs females or fathers vs non-fathers, contrary to what was found in TX. However, SD mothers did call more and stayed closer to snakes than did SD non-mothers. All SD adult sex-parental classes spent less time dealing with snakes after the emergence of pups, which was not observed in TX. The primary difference between the two populations was the behavior of TX males who spent a great deal of time harassing snakes. SD adults behaved most like TX females in that these groups spent little time actively dealing with snakes. Pups in both populations behaved similarly. These results are interpreted in terms of the relationship between potential predator and potential prey.     

Metabolic diversity in oceanic animals

Relatively little overlap exists in faunal assemblages in the oceanic waters found north of, and over the reef-like structure south of, Cape Hatteras, North Carolina, USA. To better understand the mechanisms influencing the zoogeography of these animals, metabolic-temperature patterns have been characterized for both larvae and adults of animals collected in waters north and south of Cape Hatteras and from the Caribbean Sea. Southern affinity species from north of Cape Hatteras are the most metabolically labile of the groups, based on seasonal and laboratory-acclimated studies. Adults having a northern affinity found north of Cape Hatteras are metabolically depressed at high temperatures, whereas species from the reef area and the Caribbean are metabolically depressed at low temperatures. Metabolic rates of first stage zoea of crabs from the reef area are depressed at lower temperatures than larvae of the same stage of other species of crabs from the Cape Hatteras region or the Caribbean Sea.Supported by Grant NSF GB 7435 from the National Science Foundation. The authors thank Duke University Marine Laboratory and the Cooperative Program of Biological Oceanography for the use of the R.V. Eastward. The Co-operative Program is supported through the National Science Foundation Grant GB-8189.     

Significance of nanoplankton in the Chesapeake Bay estuary and problems associated with the measurement of nanoplankton productivity

Over a 2-year program of monthly cruises covering the entire Chesapeake Bay (USA), the phytoplankters which passed 35 μm mesh were responsible for 89.6% of the phytoplankton productivity. On a single summer cruise, the <35 μm phytoplankton fraction was responsible for 93.4% of the chlorophyll a and 100% of the primary productivity. The <10 μm fraction was responsible for 81.3% of the chlorophyll a and 94% of the productivity. The difference in biomass in the <35 μm and the <10 μm fractions was significant (P=0.025), but no significant difference in the productivity could be demonstrated. Laboratory experiments demonstrated that recently assimilated carbon can be lost with gravity screening. Considering both this and the effect of herbivorous zooplankters enclosed in productivity incubations, a prescreening rather than postscreening technique is recommended for studying nanoplankton productivity.     

Self-monitoring of reproductive success: nest switching in the redlip blenny (Pisces: Blenniidae)

Summary In the redlip blenny Ophioblennius atlanticus, commonly found on Caribbean reefs, eggs are laid in a male's nest and are guarded by the male until they hatch as planktonic larvae. Male reproductive success, defined as the number of egg batches hatched per reproductive period, was positively correlated with male size and with the inner surface area of the male's nest. Male blennies often switch nests between reproductive periods. Most nest switching (83%) occurred following periods of low reproductive success. Moreover, a male having low reproductive success was more likely to switch if the inner surface area of his nest was small. Most nest switching (72–80%) was to a nest of larger surface area than the previous nest. In 72% of all switches, males had higher reproductive success in the period following the switch than in the one preceding it. The results suggest that male redlip blennies monitor their current reproductive success and the characteristics of their current nests, switch to better nests if their reproductive success is low, and typically benefit from the decision to do so. These capabilities have seldom been demonstrated in any phylum.