Biodeposition by salt-marsh invertebrates

The importance of salt-marsh invertebrate biodeposits in biogeochemical cycles is discussed. Yearly biodeposition rates of nitrogen, phosphorus, potassium, magnesium, maganese, copper, zinc, and molybdenum are reported for 5 invertebrate species. The 5 species (Littorina irrorata, Arcatula demissa, Polymesoda caroliniana, Uca pugnax and U. pugilator) deposit 1709 g dry weight m² year^-1, of which 455 g m² year^-1 is organic material. Calculations suggest that the invertebrates are capable of processing 53% of the marsh's yearly production, but the actual amount utilized is probably substantially less than this.Contribution No. 716 from the Virginia Institute of Marine Science, and Contribution No. 295 from the University of Georgia Marine Institute.     

Temperature-time relationships for survival of embryos and larvae of Mulinia lateralis (Mollusca: Bivalvia)

The influence of temperature over 8 time intervals on survival of cleavage stages, trochophore larvae, and straighthinge veliger larvae of Mulinia lateralis (Say) was investigated using a thermal gradient apparatus. There was a direct relationship of mortality with increased period of exposure. As the clams aged, temperature tolerance increased, with cleavage stages being most sensitive to higher temperatures and straight-hinge larvae least sensitive. Multiple-regression equations were developed to allow prediction of percentage mortalities under different conditions of temperature and time exposure. Entrainment of M. lateralis embryos and larvae in the cooling-water systems of steam-electric power plants should be as short as possible to keep mortality toa minimum.Contribution No. 550 of the Natural Resources Institute, University of Maryland, and Contribution No. 531 of the Virginia Institute of Marine Science.     

Ecological investigations of the marine nematode Metoncholaimus scissus

Significant concentrations of the large oncholaimid Metoncholaimus scissus Wieser and Hopper (1967) (>7000 animals/24 cm² area or 2.68x10⁶ specimens/m²) have been noted in soft-bottom turtle grass communities. Activities of the nematode frequently show an indirect relationship to blooms of the benthic diatom Pleurosigma balticum. Analysis of biomass data for M. scissus (as much as 28 g wet weight/m²) demonstrate the importance of microsite activity and sensitivity of the species to small significant changes in the benthic environment.This work was supported by grant GM 12824 from the National Institutes of Health to the Institute of Marine and Atmospheric Sciences, University of Miami. Contribution No. 1188 from the Institute of Marine and Atmospheric Sciences, University of Miami and from the Entomology Research Institute, Research Branch, Canada Department of Agriculture, Ottawa.     

Setting of the American oyster Crassostrea virginica in the James River,Virginia, USA: temporal and spatial distribution

Setting of larvae of the oyster Crassostrea virginica was monitored in the James River, Virginia, USA from 1963 to 1980. Setting patterns were similar in two ways to those described prior to 1960 (before the onset of the oyster pathogen Haplosporidium nelsoni (MSX) in Chesapeake Bay): (1) setting intensity (average number of spat per shell) was greater at stations in the lower than upper estuary, and (2) on the average, 60 to 80% of the total annual set at each station occurred during a 6-week period from mid-August through September. However, annual setting intensity from 1963–1980 was lower than previously recorded, and annual sets occurred as a series of discrete pulses rather than continuously throughout the season. Pulses were each approximately 1 to 2 weeks in duration and separated by a period of diminished or no setting. Cross-correlation analysis of annual setting patterns among stations revealed three zones in the James River: the upper estuary and entire southwest side, the lower estuary, and a mid-estuary transition zone. Setting pulses tended to be synchronous at stations within each zone, but occurred 1 to 2 weeks later at stations in downriver than in upriver zones. The location of zones is related to known aspects of water circulation in the James River estuary. Moreover, pulse setting itself may be related to the absence of strong vertical salinity gradients accompanying the fortnightly stratification-destratification process.Contribution No. 1213 from the Virginia Institute of Marine Science, School of Marine Science, The College of William and Mary     

Salinity and substratum effects on condition index of the bivalve Rangia cuneata

The condition index (CI) of the clam Rangia cuneata was measured monthly at 8 stations in 2 substrate types and 3 salinity regimes in the James River estuary, Virginia, USA. CI was higher in clams from sand bottoms than from mud, and decreased in both substrata in fresher water. Values were lowest in early spring and at a maximum in early autumn, with a pronounced autumn peak in the sand substratum. This pattern coincided with the annual salinity cycle. A field experiment showed that some factor associated with the water overlying a sand or mud substratum, rather than the nature of the substratum itself, was important in determining CI. The hypothesis is presented that this factor may be the higher suspended solids concentrations measured immediately over mud bottoms.Virginia Institute of Marine Science Contribution No. 782.     

Faunal variation on pelagic Sargassum

Pelagic Sargassum was collected in late summer, late winter, and early and late spring from inshore waters, the Gulf Stream and the Sargasso Sea of the Western North Atlantic Ocean. The noncolonial macrofauna was picked from the weed samples. The 34 samples contained 67 species and 11,234 individuals. The Shannon-Wiener index of diversity had a mean value of 2.419±0.177 (t.₀₅s _x ^– ) and a statistical range between 1.401 and 3.437 (t.₀₅ s). Mean diversity values were not significantly different among the various sampling series, and diversity did not vary with raft volume. High diversity values were related to an equitable distribution of species resulting from a stable environment and an area low in productivity. Species composition of the Sargassum organisms varied seasonally and geographically. Animals were more abundant in the spring than in the fall samples. Samples collected on a transect in the Gulf Stream and Sargasso Sea maintained a similar faunal composition.Contribution No. 351 from the Virginia Institute of Marine Science, Gloucester Point, Virginia, USA.From a thesis submitted to the faculty of the School of Marine Science, The College of William and Mary, in partial fulfillment of the requirements for the degree of Master of Arts in Marine Science.     

Latitudinal variation in linear growth and other shell characteristics of Macoma balthica

Shells of the bivalve Macoma balthica (L.) were studied from locations throughout its geographic range on both sides of the North Atlantic. These observations were supplemented by records from the literature. North-south clines were detected in shell coloration, relative shell dimensions and shell growth parameters. Moreover, shells from the two sides of the Atlantic were so different (particularly in the south) that these populations can hardly be regarded as conspecific. It is, therefore, argued that latitudinal changes should be studied separately for the American and European populations. In America, growth rates increased continuously to the south, whereas in Europe maximal growth was observed at more intermediate latitudes.Virginia Institute of Marine Science Contribution No. 1251     

Genetic structure of giant clam (Tridacna derasa) populations from reefs in the Indo-Pacific

Large genetic differences were observed among the Great Barrier Reef (GBR), Fiji and Philippine populations of Tridacna derasa (Roding) sampled in 1989 and 1990 (Nei's unbiased genetic distance, D,=0.137 to 0.341). This result contrasted strongly with the low genetic distance (D=0.032) reported previously for the giant clam T. maxima over similar geographical scales. No significant genetic differentiation was observed among most populations from the GBR (mean D=0.007), consistent with the high gene exchange expected in this highly connected reef system. However, significant differentiation resulting from differences in the frequencies of less common alleles between the North-Central GBR and South GBR (Swain region) were observed. Historical isolation of blocks of the Central Indo-West Pacific from the GBR and present-day restrictions to gene exchange between the GBR, Fiji and the Philippines as a result of oceanographic current patterns, were thought to be responsible for the high degree of genetic differentiation of T. derasa populations. The relevance of these findings to clam mariculture and reef restocking are briefly discussed.Contribution No. 197 from the Marine Science Institute, University of the Philippines and Contribution No. 562 from the Australian Institute of Marine Science     

Filtering rates of the juvenile Atlantic menhaden Brevoortia tyrannus (Pisces: Clupeidae), with consideration of the effects of detritus and swimming speed

From July to September 1982 feeding experiments were conducted with 138-mm fork length Atlantic menhaden Brevoortia tyrannus (Latrobe) (Pisces: Clupeidae) to determine their particle size-specific feeding abilities. Monoculture clearing-rate experiments showed that the minimum size of particles filtered, the minimum size threshold, for 138-mm fish is 7 to 9 m. Filtration efficiency for three species of phytoplankton below the minimum size threshold. Pseudoisochrysis paradoxa, Monochrysis lutheri, and Isochrysis galbana, averaged 1.0% (n=14). Tetraselmis suecica, Prorocentrum minimum, and 2-celled Skeleionema costatum, phytoplankton which are larger than the minimum size threshold and smaller than the 20-m upper limit for nanoplankton, were filtered at efficiencies averaging 21% (n=24). S. costatum chains of 3 to 6 cells, prey particles exceeding the size limits of nanoplankton, were filtered at average efficiencies ranging from 22 to 84%. The mean filtration efficiency for Artemia sp. nauplii (San Francisco Bay Brand) of 36% (n=7) was lower than for smaller phytoplankton prey. The presence of detritus at concentrations usually encountered in nature enhanced filtering efficiency and lowered minimum size thresholds at which phytoplankton were retained. For small food particles, filtering efficiency decreased as swimming speed of the menhaden increased. As menhaden grow, their feeding tepertoire shifts to larger planktonic organisms.Contribution No. 1201 Virginia Institute of Marine Science     

Population studies on benthic nematodes within a subtropical seagrass community

Examination of the benthic nematode fauna of the soft surface sediments of a turtle grass (Thalassia testudinum König) bed in Biscayne Bay (Miami, Florida) has revealed a high degree of homogeneity exemplified by the dominance of four species out of approximately 100 nematode taxa from the area. The dominant species, Metoncholaimus scissus, Theristus fistulatus, Spirinia parasitifera and Gomphionema typica, regularly comprised between 87 and 95% of the total number of nematodes present in samples collected during the winter and spring of 1966. T. fistulatus showed an abundance of 56% over the course of the study, i.e., 160 samples collected over a period of 14 months. Maximal peaks in population densities were noted and correlated with physiographic alterations in the environment. The M. scissus population declined concurrent with changes in the community; at the same time, with accumulation of sediment, the Terschellingia longicaudata population increased. Ratios of species, and especially shifts in the dominantforms present, with repeated collections, are extremely useful indicators of important biological and physical changes in a particular environment. Analysis of distributional data on dominant species in 64 samples from eight closely approximated positions showed that observed temporal and spatial variations were not significant statistically at the 5% level. It is concluded that erroneous observations can be made from ecological studies based on field data derived without proper replication or consideration of seasonal factors. The latter as well as intrinsic variability within the particular locality itself contribute to the basic faunistic composition of benthic communities.This work was supported by Grant 12482 from the National Institute of Health to the Institute of Marine Science, University of Miami, and is a contribution (No. 819) from the Institute of Marine Science and from the Nematology Section, Entomology Research Institute, Research Branch, Canada Department of Agriculture, Ottawa.     

Effects of chronic oil pollution on a salt-marsh grass community

A small, naturally defined saltmarsh in Chesapeake Bay (USA) was repeatedly dosed with a No. 2 fuel oil. The production, decay rates, physical characteristics and hydrocarbon content of the dominant grass species present in the marsh were routinely monitored. Spartina alterniflora was the only grass species displaying effects of the oil dosing; this is attributed to the grass's location in the marsh. A substantial portion of the S. alterniflora in the marsh was killed by the oil dosing; the remaining portion evidenced sublethal effects including delayed development in the spring, increased density, and reduced mean weight per stem. The second annual cohort of shoots, usually produced in late summer and early fall, was suppressed almost entirely. Decay rates of S. alterniflora in the oiled marsh were higher and peaked later than decay rates in a control marsh. Oil which entered the roots and rhizomes of dead S. alterniflora was retained in a relatively undergraded state for at least 7 months after dosing stopped.Virginia Institute of Marine Science Contribution No. 945     

Cellulose degradation by Lulworthia floridana and other lignicolous marine fungi

Gravimetric analyses of cellulose (Solka Floc) utilization by representative marine Ascomycetes, including Lulworthia floridana, Lindra sp., Torpedospora sp. and Halosphaeria mediosetigera, have shown noteworthy activity based on loss of weight of cellulose by the various fungi. Particularly striking activity is evidenced by L. floridana and Torpedospora sp., with >50% cellulose degradation after 3 weeks of fungal growth. Comparable studies with the deuteromycete, Dendryphiella salina, showed >50% loss within 6 days. Dissimilar responses by various L. floridana isolates are noted. Intensive degradative activity at pH's of 6 to 8 is common along with negligible amounts of cellulase (Cx units). Adsorption of the enzyme to the mycelia or to the cellulose particles in the medium is suggested. Earlier laboratory analyses of fungal degradation of Manila cordage compare favorably with present gravimetric studies and support field observations on the significance of fungal infestation of wood, particularly that incited by the Lulworthia floridana group.This work was supported by Grant GM 12482 from the National Institute of Health and Office of Naval Research Contract No. 137-792 to the Institute of Marine Sciences, University of Miami. Contribution No. 950 from the Institute of Marine Sciences, University of Miami.     

Asexual reproduction as a means of population maintenance in the coral reef asteroid Linckia multifora on Guam

The asteroid Linckia multifora (Lamarck) reproduces by autotomy of arms. Seven phases are recognized in its asexual reproductive cycle (autotomized arms; comets; counter-comets; post counter-comet I, II and III; and disc-parents). Individuals of the comet phase represent the highest percentage for population samples collected throughout the year from several sites on Guam, indicating a continuous asexual reproduction through which populations of L. multifora are being maintained.Supported by National Science Foundation Grant GA-39948 to the University of Guam Marine Laboratory; Contribution No. 108, University of Guam Marine Laboratory. Based on a thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science at the University of Guam, USA.     

Survival and activity of the oyster drill Urosalpinx cinerea under conditions of fluctuating salinity

The effects of fluctuating salinities on the survival and activity of Urosalpinx cinerea (Say) from the James River, Virginia, USA, were observed and compared to results of similar studies at constant salinities. All experiments were conducted at summer temperatures. The lower extremes of salinity fluctuations, especially values below 9, had the greatest effect on mortality; the upper extremes may have delayed, but did not reduce, mortality. There was a characteristic 10-day mortality-free period at the start of the fluctuating salinity experiments. Mortality patterns were much different in constant salinities, where the first 2 weeks of exposure were characterized by highest mortalities. In both types of experiments, drill activity, measured by attachment, feeding, and oviposition, increased as salinities increased above lethal levels (greater than a minimum of 9). Fluctuating salinities, which approximated field conditions, affected drills differently from constant salinities and were, therefore, more realistic for study of these estuarine organisms.Contribution No. 543, Virginia Institute of Marine Science, submitted by the senior author to the School of Marine Science of the College of Williams and Mary, in partial fulfillment of the requirements for the Master of Arts degree.     

Seasonal changes in the structure of an intertidal community

Quantitative (0.25 m²) samples of macrofaunal (>1.0 mm) invertebrates were taken in each season from one habitat of an intertidal sandbar in the North Inlet estuary near Georgetown, South Carolina, USA. During all seasons the community inhabiting the sample site was numerically dominated by two species of haustoriid amphipods (Acanthohaustorius millsi and Pseudohaustorius caroliniensis). Seasonal changes at the community level were clearly controlled by the population dynamics of the numerically dominant species, and qualitative information on life histories was important to the interpretation of analyses' results.This work was supported by the Environmental Technology Center of Martin Marietta Corporation and the Belle W. Baruch Institute for Marine Biology and Coastal Research. It is Contribution No. 138 of the Belle W. Baruch Institute for Marine Biology and Coastal research.     

Trophic implications of cross-shelf copepod distributions in the Southeastern Bering Sea

Spring distributions of some numerically dominant copepods reflect associations with two distinct water masses separated along the 80- to 100-m isobaths. Seaward of this middle shelf front, the oceanic Bering Sea hosts populations of Calanus cristatus, C. plumchrus, and Eucalanus bungii bungii; Metridia pacifica, Oithona similis, and Pseudocalanus spp. are also present. The large oceanic species are much less abundant in waters shallower than 80 m where the community is seasonally dominated by smaller copepods, O. similis, Acartia longiremis, and Pseudocalanus spp. Experimental and field-derived estimates of carbon ingestion indicate that the oceanic/outer shelf copepods can occasionally graze the equivalent of the daily plant production and probably routinely remove 20–30% of the primary productivity. Conversely, stocks of middle shelf copepods rarely ingest more than 5% of the plant carbon productivity. During 45 d between mid April to late May, 1979, approximately three times more organic matter was ingested m^-2 by the outer shelf/oceanic copepod community than by middle shelf species. This imbalance in cross-shelf grazing permits middle shelf phytoplankton stocks to grow rapidly to bloom proportions, and to sink ungrazed to the seabed. Over the outer shelf and particularly along the shelf break, a much closer coupling to phytoplankton supports a large biomass of oceanic grazers. Here, copepod stocks approaching 45 g dry wt m^-2 occur in late spring as a narrow band at the shelf break.Supported by National Science Foundation Grant DPP 76-23340Contribution no. 485, Institute of Marine Science, University of Alaska, Fairbanks     

Incidence,reproduction and feeding of Stylochus zebra,a polyclad turbellarian symbiont of hermit crabs

The hermit crab Pagurus pollicaris is the common host for the polyclad turbellarian Stylochus zebra in the Atlantic coastal waters from Massachusetts to North Carolina, USA. S. zebra is reported for the first time from two other hermit crabs, Pagurus impressus and Petrochirus diogenes. It was not found with Clibanarius vittatus or Pagurus longicarpus, although the latter serves as a host along the Gulf coast of Florida. The incidence of the polyclad with P. pollicaris in Massachusetts is more than twice that in populations to the south. Multiple infestations (up to 7 worms/crab) occur in over 50% of the infested crabs from Massachusetts, but they are rare elsewhere. Worms living in clear plastic shells with crabs orient in the body whorl dorsal to the host. Egg masses of worms are cemented in the same position within gastropod shells harboring the crabs. In the laboratory, the worm feeds on the gastropod Crepidula plana, a common inhabitant of shells occupied by P. pollicaris. Its feeding behavior is described. The relationship between S. zebra and P. pollicaris appears to be generally commensalistic, but it could be more complicated if the predation of crab embryos observed in the laboratory is confirmed under natural conditions.Contribution No. 755 from the Virginia Institute of Marine Science, Gloucester Point, Virginia, USA.     

Food division within two sympatric species-pairs of skates (Pisces: Rajidae)

Food habits of two sympatric species-pairs of skates (Raja erinacea-R. ocellata and R. radiata-R. senta), which occur off the east coast of North America were investigated. Stomachs from over 1600 specimens of the 4 species were collected during winter, summer, and autumn of 1969 and the winter of 1970. Diets of R. erinacea and R. ocellata consisted largely of amphipods, decapod crustaceans and polychaetes. However, R. ocellata consumed relatively more fishes and polychaetes and less decapods than R. erinacea. These two skates ate many of the same species but in different proportions; R. ocellata tended to feed on infauna and R. erinacea tended to feed on epifauna. Food preferences of the two species may be correlated to the difference in shape of the mouth and number of tooth rows. R. radiata and R. senta both fed heavily on decapod crustaceans and euphausids, but polychaetes were relatively more important to R. radiata and mysids were relatively more important to R. senta. R. radiata had a very diversified diet and fed on both epifauna and infauna. The diet of R. senta was very restricted and consisted almost entirely of epifauna. Diets of the two species-pairs were similar, but isopods and bivalves were more important to the R. erinacea-R. ocellata pair and euphausids and mysids were more important to the R. radiata-R. senta pair. These differences may reflect differences in the benthic communities with which the species-pairs are associated. Amount of overlap in resource utilization of the pairs of skates was compared with that of some other congeneric organisms.Virginia Institute of Marine Science Contribution No. 727.     

Larvae of deep-sea fishes (Stomiatoidea) from Biscayne Bay,Florida, USA,and their ecological significance

Twenty stomiatoid fish larvae (3.1 to 21,9 mm) belonging to the genera Bathophilus, Cyclothone, and Stomias were collected in plankton nets from surface waters over depths of 3 to 4 m from Biscayne Bay, Florida, USA. The adults are mesopelagic in the open water of the Florida Current and, therefore, these larvae were presumably advected in parcels of high salinity water into the shallows of Biscayne Bay by winds, tides, or currents. The presence of these larvae suggest that sewage discharged into the Florida Current may be recycling into coastal waters as well as into Biscayne Bay.Scientific Contribution No. 1403, University of Miami, Rosenstiel School of Marine and Atmospheric Science. The support of Environmental Protection Agency Contract FW QA 18050 DIU, Water Quality Office, Division of Water Quality Research is gratefully acknowledged.     

Nucleic acid and protein levels in strobilating polyps of Chrysaora quinquecirrha and Aurelia aurita

Levels of DNA, RNA, and protein were measured in scyphistomae of the scyphozoans Aurelia aurita and Chrysaora quinquecirrha during strobilation. In synchronously developing populations of A. aurita, the amount of DNA per polyp increases 41 to 260% during strobilation, whereas RNA and protein remain relatively constant. The RNA/DNA ratio drops by about 50% during strobilation in both C. quinquecirrha and A. aurita, and protein/DNA decreases by 50% in A. aurita. Specific RNA reserves are probably not accumulated in advance of strobilation, since strobilation is blocked immediately in both species by 1 to 3 g/ml actinomycin D. The size and DNA content of polyps are usually increased by prolonged incubation at temperatures of 12° to 15°C, which facilitates strobilation; however, the RNA/DNA and protein/DNA ratios of such polyps are not significantly increased by the cold conditioning.Contribution No. 472 from the Virginia Institute of Marine Science.