Showing papers in "Marine Ecology Progress Series in 1983"

The Ecological Role of Water-Column Microbes in the Sea*

Abstract: Recently developed techniques for estimating bacterial biomass and productivity indicate that bacterial biomass in the sea is related to phytoplankton concentration and that bacteria utilise 10 to 50 % of carbon fixed by photosynthesis. Evidence is presented to suggest that numbers of free bacteria are controlled by nanoplankton~c heterotrophic flagellates which are ubiquitous in the marine water column. The flagellates in turn are preyed upon by microzooplankton. Heterotrophic flagellates and microzooplankton cover the same size range as the phytoplankton, thus providing the means for returning some energy from the 'microbial loop' to the conventional planktonic food chain.

Surface slicks associated with tidally forced internal waves may transport pelagic larvae of benthic invertebrates and fishes shoreward

Abstract: L'etude porte principalement sur le transport par les vagues internes vers le rivage de Pachygrapsus crassipes (Scripps Institution of Oceanography, La Jolla

Chemical defense and evolutionary ecology of dorid nudibranchs and some other opisthobranch gastropods

Abstract: In the evolution of dorid nudibranchs and some other opisthobranch gastropods loss of the shell is correlated with the presence of defense mechanisms based upon chemicals derived from food. The chemicals are present as the result of adaptations, not by accident. Chemical defenses were preadaptive, enabling the animals to dispense with the shell. They have been gradually elaborated and made more effective, occasionally leading to de novo synthesis, independent of diet. Food dependencies have constrained the adaptive radiation of oplsthobranchs, and this may reflect relatlonshlps to predators as well as prey. For the opisthobranchs considered here, distastefulness is often combined with conspicuousness (aposematic coloration): since these animals do not occur in family groups, the aposematic coloration must have evolved without kin-selection.

RNA/DNA ratios and DNA concentrations as indicators of growth rate and biomass in planktonic marine organisms

Abstract: RNA and DNA concentrations were measured by a modification of the ethidium bromide method in batch cultures of marine phytoplankton and in natural plankton populations (1 to 333 v) from Dabob Bay, Washington State, USA, in spring and summer of 1981. In the cultures the DNA/C ratio remained nearly constant during all phases of growth and growth rate was linearly related to the RNA/DNA ratio. The DNA/C ratio and the relationship between growth rate and RNA/DNA ratio for cultures was used to estimate the amount of living biomass and the growth rates for plankton populations of Dabob Bay. The amount of living carbon was never < 57 % of the total particulate carbon and average growth rates ranged from (0.3 divisions d' to >4 divisions d-'. Some of the potential problems with such calculations, for example, occurrence of detrital DNA, variability in the DNNC ratio for different groups of organisms, and differences in the relationship between growth rate and RNA/DNA ratio, are discussed. However, these problems may not be major obstacles to using DNA concentrations and RNNDNA ratios for answering major questions in biological oceanography.

Overwintering of Calanus finmarchicus and Calanus helgolandicus.

Abstract: Overwintering of Calanus finmarchicus and C. helgolandicus was studied in the field and in laboratory experiments in a shallow (120 m) Swedish fjord and in a deep (650 m) Norwegian fjord. In the Norwegian fjord 2 populations were found in late summer and autumn: in the surface layer the copepods were smaller and more active with high respiratory and digestive enzyme activities. The deep population, consisting of Copepodid stage V (CV) and a few females, was torpid, had large oil sacs and empty guts. Their respiratory and digestive enzyme activities were very low. In the Swedish fjord CV in deep layers weighed much less than those in the Norwegian fjord. Weight-specific respiration was intermediate between deep and surface population in the Norwegian fjord. It is concluded that overwintering copepodids do not feed. Metabolic rates allowed successful overwintering only in the Norwegian fjord. Experiments performed on several occasions during overwintering witnessed - in contrast to the situation in field populations - increased rates of respiration and moulting. Mortality during moulting and time span between capture and onset of moulting decreased during autumn and winter. These observations suggest internal development during overwintering.

Phosphorus and nitrogen nutritional status of a northern australian mangrove forest

Abstract: Three sites along a 400-m transect within a tropical mangrove forest in northern Australia were monitored at monthly intervals for 12 mo to determine mangrove response to soil ammonium or phosphate enrichment. Growth response was monitored by measurement of interpetiolar stipule fall, a litter fall component which has been found to be highly correlated with new leaf appearance. Regression slopes for the cumulative stipule fall-time data for each site (2 replicate catchers per site) were used to estimate average stipule fall rates over the treatment year. These were compared with the rates obtained for the identical catcher pairs from a previous year when no treatment was applied. Similar between-year comparisons for 3 corresponding control sites, with no treatment either year, showed no significant changes in stipule fall rates (p > 0.17 in all cases). At the first treatment site, at low elevation within the intertidal zone, no significant response (p = 0.53) to P enrichment was found. For a higher elevation site, 170 m from the nearest tidal channel edge, a significant (p = 0.017) response to P enrichment was recorded, consistent with previous findings of chronically low soil extractable P at the higher elevation sites compared to the lower elevation (edge) sites (5 vs. 14 pg P g-'). A significant response (p = 0.018) to soil ammonium enrichment was found at the third (edge, low elevation) site. As the average soil ammonium level at this site was slightly but significantly higher than for all other sites, it appears that nitrogen limitation is common throughout with phosphorus limitation also evident at the higher elevation areas. Foliar analyses showed that mature Rhizophora leaf nitrogen and phosphorus levels were highly significantly correlated with average soil ammonium and extractable phosphorus respectively. Mature leaves are therefore likely to be useful indicators of mangrove forest nutritional status in remote area surveys. Newly formed leaves showed much higher N and P levels and the leaf parameters showed a complex set of correlations with other soil factors such as redox potential and salinity.

Objective selection of sensitive species indicative of pollution-induced change in benthic communities. 2. Data analyses

Abstract: An objective technique for identifying potential indicator species using analyses based on the distribution of individuals among species is presented. Benthic community data from 6 different areas in N. W. Europe are analysed. In each case species indicative of environmental change in the area are identified, even from areas where such changes are small and have resulted only in minor perturbations in the local community structure. It is shown that particular species groups are characteristically indicative of each area, and that ubiquitous indicator species comnlon to many areas do not occur. The method is rapid and involves little computation; it is robust and can be used across a range of sample sizes; it is theoretically sound and allows the objective selection of species useful as indicators of pollutant effects.

Life histories and abundance patterns of colonial corals on Jamaican reefs

Abstract: Etudes entreprises de 1977 a 1979 dans la Discovery Bay pour elucider les mecanismes controlant les modalites d'abondance sur substrats naturels ou experimentaux des coraux coloniaux. On en conclut la necessite de considerer les processus a long terme et les evenements peu frequents dans la determination de l'abondance des organismes coloniaux a grande longevite

Abundance, Species Composition and Feeding Impact of Tintinnid Micro-Zooplankton in Central Long Island Sound

Abstract: Abundance and composition of tintinnid and phytoplankton species were followed in central Long Island Sound from August 1979 to October 1980. In all, 28 tintinnid species were observed; the greatest diversity occurred between September and April. Highest tintinnid concentrations occurred in summer, with concentrations of 103 or more individuals I-' observed only when nanophytoplankton concentrations equalled or exceeded 1.3 X 105 cells I-'. Although necessary, the occurrence of small food, alone, was not a sufficient condition for high tintinnid densities. Tintinnids in central Long Island Sound exhibited the same order of magnitude yearly community ingestion rates as did the copepods. The tintinnids were responsible for removing approximately 27 % of the annual primary production from thls region. It is concluded that tintinnids are an integral part of the Long Island Sound plankton community, equal in importance to copepods.

Effects of recurrent sand deposition on rocky intertidal organisms: importance of substrate heterogeneity in a fluctuating environment

Abstract: This research represents a 3-yr (September 1975-June 1978) examination of a southern California rocky intertidal system influenced by variable sand deposition ranging from almost zero to total seasonal inundation over different portions of the study area. An apparent subclimax association of opportunistic macrophytes (Chaetomorpha linum, Cladophora columbiana, Ulva lobata, Enteromorpha intestinalis) and highly-reproductive macroinvertebrates (Tetraclita rubescens, Chtharnalus fissus/dalli, Phragmatoporna californica) dominate by rapidly repopulating those lowlying microhabitats routinely buried by sand. Refuge habitats on slightly elevated rock pinnacles (sand free) were dominated by long-lived molluscs such as Mytilus californianus, Haliotis cracherodii and Lottia gigantea. The lower limits of these biotically-competent taxa (sensu Vermeij. 1978) appear to be determined by the physical smothering action of sand, rather than by the kinds of biological factors documented for other rocky intertidal habitats. The stress-tolerant Anthopleura elegantissima dominates the upper intertidal macroinvertebrate cover because of reproductive, behavioral and physiological adaptations to the stresses of aerial exposure and sand burial. The dominant plant in lower intertidal pools is the biotically-competent Phyllospadix scouleri that tolerates sand because of its large size and its rhizomatous root system which traps and binds sediments. The most numerous of the mobile macroinvertebrates. Tegula funebralis, is able to migrate away from the winter sand inundation to refuge habitats. The research reported here suggests that, with few exceptions, sand-stressed habitats primarily serve as important refuges for 2 functional groups of species: stress-tolerant strategists and opportunistic strategists.

Factors affecting phytoplankton extracellular release in the Southern Bight of the North Sea

Abstract: Phytoplankton extra cellular release of organic substances was studied in the Southern Bight of the North Sea in relation to changes in growth conditions (light intensity and inorganic nitrogen concentration) and in taxonomie phytoplankton composition. Light intensity had no effect on percent extracellular release (PER). A high negative correlation between PER and mineraI nitrogen concentration was found during spring bloom wh en phytoplankton were dominated by flagellates (Phaeocystis poucheti in the Southern Bight; dinoflagellates in the oligotrophic English Channel). The physiological response of the flagellate.populations to shortage of nutrients differed. High PER was measured during the decline of the bloom with lower values in oligotrophic (46 %) than eutrophie waters (70 to 80 %). On the other hand, no significant correlation was found between PER and mineraI nitrogen for diatoms which dominate the phytoplankton population outside the spring period. PER values were unchangeably low (0 to 14 %) over a large range of mineraI nitrogen concentrations (0 to 50 µg at N 1-1).

Community structure, succession and development of coral reefs in Hawaii

Abstract: Reef building corals in the Hawaiian Archipelago consist of only 42 species belonging to 16 genera. The Hawaiian coral fauna is highly depauperate relative to the Indo-West Pacific Ocean, a result most likely due to geographic isolation. Although impoverished, the species composition of reef building corals is remarkably uniform throughout the archipelago. Differences in species composition which do exist appear to be caused by varying patterns of disturbance and recruitment. Although patchy distributional patterns exist within islands, the differences in species composition between islands are small. Where adequate substrata prevail within the euphotic zone most species are present. Hence species composition tends to be an all or none phenomenon. Contrary to most terrestrial ecosystems, a positive correlation does not exist between species richness and habitat area (0 to 20 m). This may be due to low habitat complexity within the zone for reef building corals and high rates of recruitment between islands. It also suggests that most reef building corals in Hawaii are generalized species. The fact that most do not drop out moving northwestward in the chain is evidence of their generalized life history (eurytopy). The most significant differences between coral reefs found on different islands, are differences in community structure. On seaward reefs differences in community structure appear to be primarily caused by differences in physical disturbance from long period swell; they can be interpreted as differences in successional age. Moving northwestward within the chain, coral growth rates steadily decline. This has the effect of lengthening the successional process and increasing the likelihood of intervening disturbance. A hypothetical model operational over generations is presented demonstrating the effect of disturbance on the successional process for coral reefs in general. The development of large-scale morphological features such as spurs and grooves, fringing and barrier reefs and atolls involve processes operational over geological periods of time. The chronology of the Hawaiian Archipelago is now sufficiently well known to serve as a time scale against which the development of these structures can be measured.

Comparative ecology of nekton residing in a tidal creek and adjacent seagrass meadow, community composition and structure

Abstract: A structural analysis of the nekton communities occupying a tldal creek and adjacent seagrass meadow at Vaucluse Shores, Virginia (Delmawa Peninsula, USA) is presented along with a comparison of the relative value of each habit to the early life stages of marine and estuarine species. Seagrass meadows were characterized by significantly greater richness and diversity of constituent taxa; both areas, nevertheless, contained mixtures of habitat specialists and wide-ranging (ubiquitous) species that displayed no area1 preferences. Except for a few resident forms, much of the nekton community in the grassbed was comprised of less abundant 'southern' species that entered the Chesapeake Bay in late summer and fall. Reciprocal averaging and numerical classification procedures applied to pooled station collections further indicated the clinal nature of species distributions among habitats, but also clearly demonstrated several microhabitat associations for either the Zostera marina or Ruppia maritima portions of the grassbed. The sciaenid. Leiostomus xanthurus dominated the nekton in both habitats, with > 80 % of all individuals but were nearly 4 times as abundant in the tidal creek. Abundance distribution and length frequency analyses for this species indicated that the marsh is the preferred habitat but also that larger individuals in the population continuously 'bled off' into downstream areas. Two other species of regional importance. Callinectes sapidus and Paralichthys dentatus, also utilized both habitats extensively. Late in summer and early fall, juveniles of both species were more abundant in the grassbed, whereas earlier in the year, they were randomly dispersed. The apparently limited dependence on both the grassbed and tidal creek by the young of local taxa is strikingly different when compared to similar habitats at lower latitudes. In light of the differences established between these habitats and their utilization by different species, an attempt is made to identify potentially important determinants of community structure and relate these to the success of individual populations in both areas. Because few expenmental data are available, our presentation, by necessity, is hypothetical.

Phyto-Zooplankton Community in Coastal Waters of Western Sweden -An Ecosystem Off Balance?

Abstract: ABSTFUCT: A baseline study of the phytound zooplankton community was carried out from 1978 to 1981 in, what was supposed to be, a relatively undisturbed fjord on the west coast of Sweden. Heavy phytoplankton blooms were found during spring and autumn. Chlorophyll a and cell numbers were far above normal. Extremely low zooplankton biomass during the spring bloom and high abundance of scyphomedusae (which preyed on zooplankton during the summer) resulted in low grazing pressure and probably led to increased sedimentation of organic matter. Oxygen deficit has occurred in bottom waters of the fjord in the absence of adequate exchange. It was not possible to determine whether this series of events is due to natural fluctuations or man-made influences.

Latitudinal limits of coral reef growth

Abstract: In the Abrolhos Islands, site of a high-latitude coral reef, the net rate of community calcification is high but growth of frame-building corals is reduced. Our studles suggest that the latitudinal limits of coral reef development are often set by competition of macroalgae with corals, and that macroalgae are favoured at these latitudes by high nutrient concentrations, moderate water temperatures (for macroalgae) and possibly by reduced grazing pressure, while coral growth is reduced by temperatures which, for reef corals, are low.

Quantitative relationships between phytoplankton, bacteria and heterotrophic microflagellates in shelf waters

Abstract: Estimates of the numbers and biomass of bacteria as a function of depth in coastal and upwelling waters off the western approaches to the Engllsh Channel and in the southern Benguela upwelling region off the Cape Peninsula, South Africa, show that the numbers of bacteria are correlated with the standing stocks of phytoplankton as assessed by chlorophyll a concentration. Standing stocks of heterotrophic microflagellates in the size range 3 to 10 pm, amount to some 16.9 % on average, of bacterial standing stocks (mg C m-3) estimated by direct microscopy. Calculations of carbon flow through the microheterotrophic consumer community suggest that approximately 20 to 60 % of primary production, posslbly representing the dissolved components leaching out of, and lost from phytoplankton cells during zooplankton grazing, enters the microbial food chain. Much of this appears to be dissipated by bacteria, with some 5.2 to 8.1 % of the photoassimilated carbon being incorporated into bacterial carbon production. At least 66% of this is exploited by the heterotrophic n~icroflagellates leaving a maximum of 34 % of bacterial production for the larger bactivorous suspension feeders

Effects of fish grazing and damselfish territoriality on coral reef algae. I. Algal community structure

Abstract: An experiment was performed on Britomart Reef (central region, Great Barrier Reef) to determine the effects of fish grazing and territoriality by the damselfish Hemiglyphidodon plagiometopon on benthic algal community structure. This pomacentrid excludes herbivorous fish from its territory, creating undergrazed patches with characteristic 'algal lawns' within coral reef lagoons. Pieces of natural coral substratum were placed at a depth of 10 m under 4 sets of treatments: within cages protected from fish grazing, within damselfish territories, within shaded damselfish territories, and outside temtories exposed to natural levels of fish grazing. A reduction in grazing by herbivorous fish, caused by caging or by the territorial behaviour of H, plagiometopon, resulted in marked changes in algal community structure. After 3 to 4 mo, the response of algal abundance and community structure to the treatments was highly variable. After 11 to 12 mo, however, decreased fish grazing was found to cause a significant increase in algal biomass and percent-cover. Algal species diversity (H',, and number of species) was relatively high wlthin damselfish territories, while diversity within cages and on substrate fully exposed to fish grazing was relat~vely low. Thus, species diversity was maximized at intermediate levels of accessibility to fish grazing. Algal species composition also shifted with accessibility to fish grazing. The algal community within cages was dominated by rhodophytes, particularly Polysiphonia subtilissima. Damselfish territones were dominated by a mixture of rhodophytes and cyanophytes, including Centroceras clavulatum, Gracilarjopsis rhodotricha, and Lyngbya aestuarii. Species composition within shaded territories was intermediate between these 2 treatments, exhibiting affinities to both. The naturally grazed algal community outside the damselfish territory was dominated by filamentous cyanophytes such as L. aestuarii and Symploca hydnoidesand by the encrusting chlorophyte Pseudendoclonjum sp. The interstices of the coral substratum were found to be riddled with S. hydnoides, L. convervoides, Oscillatoria aff. amphibia, and 0. aff nigroviridis. Cyanophytes clearly dominated substratum exposed to natural levels of fish grazing. It is suggested that rates of nitrogen fixation on natural coral reef substratum are positively related to levels of fish grazing.

Comparative feeding of three species of larval fishes in the northern Gulf of Mexico: Brevoortia patronus, Leiostomus xanthurus, and Micropogonias undulatus

Abstract: The diets of larval gulf menhaden Brevoortia patronus, spot Leiostomus x d n t h u ~ s , and Atlantic croaker Micropogonias undulatus, collected in the northern Gulf of Mexico in December 1979, February and December 1980, and February 1981, were significantly (P<0.001) different when compared with respect to length by step-wise discriminant analysis, and there was little overlap when the diets of size-specific larvae that CO-occurred in discrete collections were compared by percentsimilarity. Gulf menhaden larvae had a more diverse diet that included phytoplankters (diatoms and dinoflagellates) as well as zooplankters (tintinnids, pelecypods, pteropods, and all stages of copepods). The diets of larval spot and Atlantic croaker were largely restricted to zooplankton. Overall diet distinctiveness, the lack of diet overlap, and the lack of small-scale CO-occurrence indicate that the larvae of these three species do not compete for food.

Phytoplankton release of extracellular organic carbon, molecular weight composition, and bacterial assimilation

Abstract: Phytoplankton release of extracellular dissolved organic carbon (EOC) and its subsequent assimilation by planktonic bacteria was quantified using the procaryotic inhibitor streptomycin. The carbon flow was assayed in the Danish estuary. Randers Fjord, and in laboratory experiments. From 34 to 90 % of the released carbon was transported to the bacteria; the bacterial metabolism of EOC ranged from 3 to 30 % of total primary production. If no correction for bacterial respiration (20 to 50 Oh) is made the EOC transport can be seriously underestimated. The released products were predominantly of low molecular weight (< 900 Daltons). The bacteria showed distinct selectivity for these small molecules. Streptomycin, an active bactericidal agent, also affected algal photosynthesis in some cases. In carbon flow experiments antibiotics must be used with great care.

Reproductive strategies in two closely related stony corals (Agaricia, Scleractinia)

Abstract: Etude comparative chez Agaricia agaricites et A. humilis montrant que les differences de strategie reproductrices peuvent s'expliquer en relation avec la possibilite de predire leur habitat (collectes effectuees sur deux ans sur le recif frangeant de Curacao)

Production, Predation and Food Niche Segregation in a Marine Shallow Soft-Bottom Community

Abstract: A shallow soft bottom in Gullmar Fjord (Sweden) was investigated in order to determine the impact by epibenthic predators and possible competition for food between CO-occurring shrimp and fish species. Large numbers of the shrimp Crangon crangon, juvenile plaice Pleuronectesplatessa and sand goby Pornatoschistus rninutus aggregated during summer in shallow areas and fed on benthic macroand meiofauna. Predation impact was calculated using estimates of gross production efficiencies and productlon rates. In 1976 and 1977, yearly predation amounted to 12 and 17 %, respectively, of the total macroand meiofauna productlon. The low exploitation rate of the benthic community contradicts the hypothesis that predation should be the major extrinsic determinant keeping population levels below the carrying capacity of the environment. Shallow soft bottoms provide an abundant food supply that will neither limit growth nor produce severe competition between the epibenthic predators, although their diets are almost identical. It IS suggested that larger predators will control the abundance of epibenthic feeders such as shrimp, gobies and small flatfish inhabiting shallow water.

Oxygen and inorganic nitrogen contents and fluxes in burrows of the shrimps Callianassa japonica and Upogebia major

Abstract: Concentrations of dissolved oxygen and inorganic nitrogenous compounds in burrows occupied by the shrimps Callianassa japonica (de Haan) and Upogebia major (de Haan) were compared to those in the overlying waters under simulated in situ conditions. Dissolved oxygen content in the burrow was considerably lower; it ranged from 12 to 45 % of saturation values for C. japonica burrows and from 30 to 41 % for U. major burrows respectively. One order of magnitude higher values for ammonium and 2 to 3 times higher nitrate plus nitrite values, compared to overlying waters, were also observed. Both oxygen and inorganic nitrogen data indicate that the burrow water is distinctively different from overlying waters and forms a unique microenvironment for benthic microorganisms. Estimated rates of irrigation by the burrowing shrimps, based on the oxygen balance in the burrow at 20.5 \"C, were 32 to 89 m1 h-' for C, japonica and 14 and 33 m1 h' for U. major. Our data suggest that the burrow, formed and maintained by the burrowing shrimps, has roughly the same oxygen consumption and ammonium production as the surrounding sediment surface, the metabolically most active site in the sediment.

Fluid mechanical aspects of suspension feeding

Abstract: Most accounts on suspension feeding assume that mechanical, sievelike filters retain particles from the ambient water Fluid mechanical aspects have been neglected. Suspension feeding is characterized by very low Reynolds numbers. This implies that water processing and particle retention are exclusively determined by viscous forces. Modern filtration theory can therefore be applied to hypotheses on suspension feeding involving mechanical filters. The resistance to water flow through such filters was found to correspond to pressure drops across the filters of about 0.1 to 0.4 mm H,O in flagellates, ciliates, sponges, and ascidians; and of > l mm H,O in copepods and bivalves. These theoretical pressure drops are consistent with the function as filters of ciliate membranelles, pseudopodial collars in flagellates and sponges, and ascidian mucus filters. Ciliary and flagellar water transport operate at very low pressures The pressure drops calculated for copepod second maxillae and bivalve laterofrontal cirri seem to be incompatible with the roles as filters traditionally ascribed to these structures. Recent studies indicate that sievelike models have to be abandoned in explaining particle retention in copepods and bivalves. Particles seem to be captured by means of mechanisms that do not imply physical interception of the suspended particles Copepods seem to have adopted mechanisms, based on viscous forces, that direct food particles in the surrounding water toward the second maxillae, which eventually capture the parcel of water that contains the particle. In the bivalve gill capture of suspended particles implies transfer from the currents passing through the gill via the interfilamentary spaces to the frontal surface currents along the filaments. Complex patterns of flow arise where the 2 systems of currents meet at the entrance to the interfilamentary spaces. The patterns are characterized by steep velocity gradients which may act on suspended particles and cause them to enter the surface currents, i.e. to be captured. It remains to be ascertained to what extent fluid mechanics operate in the capture of particles in other metazoan ciliary feeders

Bacterial production in marine sediments: will cell-specific measures agree with whole-system metabolism?

Abstract: Estimates for bacterial production in nearshore western Atlantic Ocean sediments were made using the frequency of dividing cell and thymidine uptake methods. The frequency of dividing cell (FDC) method resulted in estimates in the range of 5 to 50 g C m-' d-'. The thymidine uptake (THY) method resulted in estimates of 1 to .8 g C mP2 d-'. Metabolic measurements based on sediment oxygen uptake show that the FDC estimates are unreasonably high, while THY estimates, which have been corrected for DNA extraction and thymidine dilution, are reasonable w ~ t h respect to oxygen uptake data. Problems associated with these 2 bacterial production methods when used in sediments are discussed.