Showing papers in "Marine Biology in 1975"

Measurements of electron transport activities in marine phytoplankton

Abstract: A simple and sensitive spectrophotometric method of measuring electron transfer in the transport system (ETS) in marine phytoplankton has been developed and characterized. The assay is based on the reduction of the tetrazolium salt 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT) by homogenates in the presence of the nonionic detergent Triton X-100. The simplicity and sensitivity of this assay have considerable advantage over existing methods of measuring ETS activity in marine samples where numerous assays must be rapidly carried out on samples which often demonstrate low activities. Several established substrates and inhibitors of electron transport in the ETS were investigated, and each is discussed in relation to the site of INT reduction in the diatoms Skeletonema costatum and Chaetoceros debilis and in the unicellular green alga Dunaliella tertiolecta. The results from these studies suggest that the maximum rate of electron transport, Vmax, is measured in each case.

The measurement of respiratory electron-transport-system activity in marine zooplankton

Abstract: A modification of the tetrazolium reduction method (Packard, 1971) for measurement of respiratory electron transport system activity in marine zooplankton is described. A major modification is the addition of Triton X-100 to the reaction mixture to solubilize formazan produced, thus eliminating an organic extraction step and increasing the sensitivity and versatility of the method. The kinetic parameters of the assay are presented and the apparent effects of Triton X-100 are discussed. The correlation between electron-transport-system (ETS) activity and in vivo respiration (ETS/R) for Calanus pacificus has been found to be 2.02±0.29 (standard deviation). The method is presented as providing a reliable estimate of the zooplankton component of oxygen consumption in the sea.

Impact of sewage on the distribution, abundance and community structure of rocky intertidal macro-organisms

Abstract: The biological effects of a low-volume domestic sewage discharge were studied near Wilson Cove, San Clemente Island, California (USA), from February to June, 1972. There were fewer species and less cover near the outfall (7 macro-invertebrates, 17.6%; 13 macrophytes, 91.7%) than in nearby “unpolluted” control areas (9 macroinvertebrates, 9.2%; 30 macrophytes, 103.4%). The outfall biota was less diverse than that of the controls, as shown by 5 different diversity indices. A great reduction in community stratification (spatial heterogeneity) and, hence, community complexity occurred near the outfall; this reduction in stratification was primarilly due to the absence of Egregia laevigata, Halidrys dioica, Sargassum agardhianum and Phyllospadix torreyi. These were replaced in the mid-intertidal near the outfall by a low turf of blue-green algae, Ulva californica, Gelidium pusillum and small Pterocladia capillacea, and in the lower intertidal by Serpulorbis squamigerus covered with Corallina officinalis Var. chilensis. A statistically-based determination of assemblages or groups of organisms (i.e., cluster analysis) revealed 3 discrete outfall and 3 discrete control area groups; 3 assemblages contained samples from both areas. The distributional patterns of these groups indicate that near the outfall the degree of dilution of discharged sewage is more important in regulating zonation than is tidal height. The enhancement of the suspension feeder Serpulorbis squamigerus and the omnivores Ligia occidentalis, Pachygrapsus crassipes and Anthopleura elegantissima in the outer fringe of the outfall plume hypothetically is due to their ability to utilize sewage as a food source. A critical effect of the outfall may be to decrease environmental stability thereby favoring rapid-colonizers and more sewage-tolerant organisms. The outfall macrophytes were characterized by relatively higher net primary productivities, smaller growth forms, simpler and shorter life histories, and most were components of early successional stages.

Particle size-selection of two deposit feeders: the amphipod Corophium volutator and the prosobranch Hydrobia ulvae

Abstract: The feeding biology of the deposit-feeding amphipod Corophium volutator is compared to that of the coexisting, deposit-feeding prosobranch Hydrobia ulvae. Regarding ingestion of particles, both forms show size selection which alone can explain their coexistence. Particle size-selection also explains some qualitative differences in the composition of the food of the two forms; thus, diatoms play a relatively larger role in the diet of H. ulvae than in the diet of c. volutator, whereas bacteria are probably relatively more important for the latter. Results of experiments with feeding of C-14 labelled microorganisms are in accordance with the findings on particle size-distribution of the gut contents, and show that (1) C. volutator can only utilize bacteria adsorbed to particles within the size range 4 to 63 μ (this is why the presence of clay and silt particles in the sediment are necessary for efficient feeding of this amphipod); (2) C. volutator can utilize bacteria suspended in the water pumped through its burrow for respiration if silt and clay particles are present in the sediment. (3) H. ulvae can utilize large particles, and also browses on surfaces, and some evidence is brought forward that it also utilizes mucus for trapping microorganisms. The coexistence of deposit-feeding animals is discussed. It is concluded that the number of coexisting, closely related species is usually small, and that their resource partitioning is probably mainly based on particle-size selectivity. In the case of unrelated forms (e.g. H. ulvae and C. volutator, a number of behavioural, physiological and morphological differences, and also the widespread ability of deposit feeders to utilize alternative feeding mechanisms may also lead to resource partitioning. Thus, there are often several niche dimensions related to feeding allowing a certain diversity of coexisting deposit feeders.

Growth and form in the reef-building coral Montastrea annularis

Abstract: The in-situ growth rate of the reef coral Montastrea annularis on a reef at Jamaica, W. Indies was determined for a 1-year period using Alizarin Red-S staining techniques. Growth rate is correlated with water depth and growth form. The flattened growth form of M. annularis allows for continued rapid increase in colony surface area at low light intensities. The geomorphology of Jamaican reefs may in part be controlled by the population ecology of M. annularis.

Carbon requirements of a population of the estuarine copepod Eurytemora affinis

Abstract: The production of algae in the Patuxent River estuary (Maryland, USA) was much less than the carbon requirements of a population of the calanoid copepod Eurytemora affinis Detrital carbon was present in quantities that suggest turnover times of 8 to 83 days for this pool, assuming that all algal production was consumed by E affinis We hypothesize that E affinis must consume detritus to meet a part of its requirements for energy

Distribution of coccolithophores in marginal seas along the western Pacific Ocean and in the Red Sea

Abstract: The distribution of coccolithophores was studied in the neritic environment along the western margin of the Pacific Ocean: the Inland Sea of Seto, Yellow Sea, East China Sea, South China Sea, Java Sea, Timor Sea, Arafura Sea and Gulf of Carpentaria. The coccolithophore community in the Red Sea was also studied for comparison with the Pacific marginal seas. With minor exceptions, the coccolithophore communities were very similar throughout the neritic areas investigated, but differed completely from the pelagic community in three aspects. Firstly, almost all neritic coccolithophores, regardless of species, suffered various degrees and forms of malformation with relation to the morphology of their coccoliths, while such malformation was rare in the pelagic population. Nitrogen deficiency may cause such malformation. Secondly, the diversity of species in these marginal seas was much lower than in the pelagic environment, although no species was found to be exclusively neritic. Emiliania huxleyi, usually ubiquitous in oceanic areas and in various neritic environments of higher latitudes, was scarce, while Gephyrocapsa oceanica dominated the flora throughout the studied areas. Finally, the horizontal and vertical distributions of the neritic populations were sporadic compared to those of the rather uniform pelagic environments.

Influence of algal concentration and temperature on the filtration rate of Mytilus edulis

Abstract: The filtration rates of Mytilus edilis (=galloprovincialis; 40 mm) were determined in relation to food concentration and temperature, using pure suspensions of the unicellular alga Platymonas suecica in concentrations ranging from 3x105 cells/l to 1.5x108 cells/l. The rate of filtration (ml/h/mussel) generally decreased as cell concentrations increased, and dropped to low values when concentrations above 5x107 cells/l were supplied. The amount of water swept clear varied continuously, and noticeable differences in the filtration activity of M. edulis were observed over short time intervals (5 min). Fluctuations of filtered volumes per unit time were greater with lower than with higher concentrations of algae. The influence of temperature on filtration activity was highest between 5°–15°C and 25°–30°C. A temperature increase from 15° to 25°C resulted in only a slight increase in filtration rate. At 5° and 30°C, filtration dropped to very low values, namely 350 and 100 ml/h, respectively. The temperature coefficients for the filtration rates of M. edulis were determined as: Q10 (5° to 15°C)=4.96; Q10 (10° to 20°C)=1.22. The amount of algae cells ingested per mussel per hour is directly related to food concentration. The maximum number of cells filtered/mussel/h in an algal suspension of 70x106 cells/l was 21.5x105 cells/h. Cell concentrations of up to 40x106 cells/l were swept clear without producing pseudofaeces. The critical cell density for M. edulis was reached at algal concentrations of 70 to 80x106 cells/l. Above these concentrations no normal filtration activity was observed.

Brood or broadcast? The adaptive significance of different reproductive strategies in the two intertidal sea stars Leptasterias hexactis and Pisaster ochraceus

Abstract: This paper considers the adaptive significance of two different reproductive methods in two co-occurring, competing sea stars. The smaller (3 to 8 g mean wet weight) Leptasterias hexactis broods relatively few, large young in the winter, while the large (300 to 650 g mean wet weight) Pisaster ochraceus broadcasts relatively many, small eggs each spring. L. hexactis matures at a small size (2 g wet weight) in about 2 years, and P. ochraceus matures at a larger size (70 to 90 g wet weight) in about 5 years (Menge, 1974). As in many broadcasting asteroids, gonad and storage organ indices of P. ochraceus are inversely related over time, and maximum storage-organ index correlates with the summer feeding maximum (Mauzey, 1966). In contrast, both organ indices of L. hexactis and feeding increase and are positively correlated until early autumn, when feeding activity begins to decline. At this time the male gonad index continues to rise, and the storage-organ index drops. In contrast, both organ indices of females rise. Spawning occurs from November to January. Thereafter storage-organ indices decline in females, presumably because females draw upon energy reserves while brooding; storage-organ indices rise in males, presumably because males do not brood and can feed if food is available. The primary cause for the differences between annual reproductive cycles of P. ochraceus and L. hexactis is suggested to be patterns of food availability for the released young (planktonic food for the broadcasted young of P. ochraceus and benthic prey for the brooded young of L. hexactis. Estimates of pre-maturity survival and post-maturity longevity indicate that the probability of survival per individual of young P. ochraceus is vastly lower than that of L. hexactis. However, once mature, P. ochraceus has a much longer expected lifespan. Brooding is suggested to be a coadaptive consequence of competition-induced small size. Assuming planktonic mortality rates in this environment are roughly constant across broadcasting species, I suggest that a small broadcasting species could not produce enough offspring in its expected lifespan to replace itself. This hypothesis is partly supported by some simple simulations. Broadcasting is suggested to permit rapid location and utilization of spatially and temporally unpredictable, but highly desirable, resources by allowing rapid and widespread dispersal. Brooders presumably cannot disperse rapidly and must rely on more reliable, but perhaps less desirable, resources. Factors affecting reproductive patterns in marine invertebrates include (1) food availability for both adults and offspring, (2) planktonic mortality rates, (3) interactions between species and latitudinal changes in these factors, and (4) various physical factors. This paper suggests that competition and predation can have an important effect on the evolution of reproductive methods, a possibility heretofore largely ignored. Although several similar examples of co-occurring species' pairs which differ in reproductive method and size are available, the role of adult interactions is unknown in these examples.

High copper concentrations in squid livers in association with elevated levels of silver, cadmium, and zinc

Abstract: Livers from 43 Loligo opalescens, 14 Ommastrephes bartrami, and 7 Symplectoteuthis oualaniensis were analyzed for their silver, cadmium, copper, zinc and iron contents. Copper concentrations of up to 15,000 μg/g dry weight were found in L. opalescens in conjunction with significant correlations between this element and Ag, Cd and Zn. The latter elements are known to affect Cu metabolism in terrestrial organisms; however, whether the correlations occurring in marine organisms represent casual, or cause and effect, relationships is as yet unknown.

The Dynamics of Phytoplankton Blooms in Puget Sound, a Fjord in the Northwestern United States*

Abstract: This paper describes a quantitative investigation of relationships between the growth of phytoplankton, and climatic and hydrodynamci conditions in temperate fjords with marked tides, as exemplified by Puget Sound, Washington (USA). Algal growth in the open waters of the central basin of the Sound is dominated by a number of intense blooms beginning in late April or May and recurring throughout the summer. Rarely, and only briefly, does nitrate become exhausted. The phytoplankton production rate in the central basin of Puget Sound is about 465 g C m-2 year-1. During the springs of 1966 and 1967, oceanographic measurements were carried out at a mid-channel station with sufficient frequency to allow investigation of physical and biological processes with time scales of the order of a day. The principal investigative tool is a numerical model in which the hydrodynamical conditions are represented by an approximate analysis of the gravitational convection mode of circulation. Algal concentration is represented as a continous function of space and time in the model which ascribes changes in phytoplankton density to variations in photosynthetic and respiratory activity, algal sinking, grazing by herbivores, and to mixing and advection. Computations adequately reproduce the principal features of phytoplankton concentrations observed during 75 days and 35 days in the springs of 1966 and 1967, respectively. Numerical experiments assess the relative importance of various processes which govern the level of primary production in Puget Sound. It is concluded that phytoplankton growth is limited by a combination of factors, including vertical advection and turbulence, modulation of underwater light intensity by self-shading and inorganic particulates, sinking of algal cells, and occasional rapid horizontal advection of the population from the area by sustained winds. The high primary productivity of the Sound is due to intensive upward transport of nitrate by the estuarine mechanism. These results should be generally applicable to other temperate fjords because of the largely conventional choice of the biological functions.

Effect of temperature and temperature adaptation on calcification rate in the hermatypic coral Pocillopora damicornis

Abstract: Using 45Ca incorporation into the coral skeleton as a measure of calcification rate, the effect of temperature on clacification rate was studied in the hermatypic coral Pocillopora damicornis. Both immediate and long-term (adaptation) effects were investigated. Temperature has a marked effect on rate — an effect that varies depending on the temperature history of the coral (i.e., temperature adaptation occurs). P. damicornis showed both 27° and 31°C temperature optima, one or the other being dominant depending on the natural water temperature to which the coral was adapted. The two optimum temperatures may indicate two isoenzymes or two alternate metabolic pathways involved in the calcification process.

Extension rate: A primary control on the isotopic composition of West Indian (Jamaican) scleractinian reef coral skeletons

Abstract: Large variations in skeletal microarchitecture, and in the carbon and oxygen isotopic composition of the skeleton, exist within single calices and over the surfaces of single colonies of various species of West Indian (Jamaican) scleractinian reef corals. Rapidly extending parts of individual colonies are depleted in both C13 and O18 regardless of the abundance of zooxanthellae in the overlying tissues. We suggest that this relationship is due to active translocation of organic compounds to sites of rapid calcification. Considerable variation in isotopic composition is found in skeletons of different specimens of the same species even when the skeletons are sampled in a consistent manner, come from the same locality and depth, and have a comparable growth history. The isotopic composition of the scleractinian skeleton is vastly more complex than has heretofore been realized.

Energy flow through the benthos in a Scottish Sea Loch

Abstract: Analysis of material collected in settlement traps at regular intervals over a period of a year gave an estimate of the annual organic input to the bottom sediment of about 28 gC/m2 year, which is a little less than one third of the primary production in the overlying water column. The aerobic benthic community metabolism, estimated from in situ respiration measurements, was not significantly different from the carbon input. The rate of release of ammonia from the sediment was also measured in situ and would be sufficient to supply the greater part of the required input of inorganic nitrogen for photosynthesis in the water column.

Algal succession in a Macrocystis pyrifera forest

Abstract: Algal succession within a subtidal forest of the giant kelp Macrocystis pyrifera was studied by following colonization and community development on concrete blocks fastened to the bottom. Sets of blocks were placed in the bed at 3-month intervals. Subsequent algal development on each set was followed for over a year. All macroscopic species attached to the substrata were noted, and the number and lenght of basal branches determined every 1 to 3 months. Colonizing plants fell into 3 categories: rapid-growing ephemerals, and rapid and slow-growing perennials. Ephemerals such as Giffordia (Ectocarpus) mitchellae, Colpomenia peregrina, and diatom films generally produced and initial bloom on the blocks but were gradually replaced by perennials (articulated corallines, Rhodymenia spp., Gigartina spp.) characteristic of the mature kelp community. These stages, rather than representing “ecological” succession, seemed to reflect differences in growth rate and success in interspecific competition for space and light. Colonization on the blocks varied with season, indicating that most species have either a spring-summer or fall-winter period of maximum reproduction. M. pyrifera sporophyte colonization was greatest in spring. During community development, algal diversity (H), number of species (s) and evenness (J) all reached a peak within 100 to 200 days regardless of the time the blocks were started. Diversity and number of species then fell as ephemeral species disappeared. These species were apparently unable to compete with perennials and, once gone, did not recolonize. Evenness remained high.

Seasonal studies on the relative importance of different size fractions of phytoplankton in Narragansett Bay (USA)

Abstract: The composition and productivity of four different size-fractions ( 100 μm) of the phytoplankton of lower Narragansett Bay (USA) were followed over an annual cycle from November, 1972 to October, 1973. Diatoms dominated the population in the winter-spring bloom and in the fall, the summer population was dominated by flagellates. The nannoplankton ( 20 μm) were the most important. Nannoplankters domnated in the summer. The yearly mean assimilation numbers for the different fractions were not signfficantly different. During the winter-spring bloom, however, the assimilation numbers for the netplankters were significantly higher than those for the nannoplankton fraction. Temperature accounted for most of the variability in assimilation numbers; a marked nutrient stress was observed on only two occasions. Growth rates calculated from 14C uptake and adenosine triphosphate (ATP)-cell carbon were generally quite high; maxima were >1.90 doublings per day during blooms of a flagellate in the summer and of Skeletonema costatum in the fall. The series of short cycles observed in which the dominant species changed were related to changes in the physiological state of the population. Higher growth rates were generally observed at times of peak phytoplankton abundance while lower growth rates were observed between these peaks. The high growth rates and assimilation numbers usually found suggest that the phytoplankton in lower Narragansett Bay was not generally nutrient-limited between November, 1972 and October, 1973. Nutrient regeneration in this shallow estuary, therefore, must be very rapid when in situ nutrient levels are low.

Development of Contemporary Eastern Pacific Coral Reefs

Abstract: An overview of oceanographic conditions prevailing in the tropical Eastern Pacific Ocean suggests that the entire region is environmentally marginal for coral-reef development. The principal features of this environment are a strong, permanent, shallow thermocline and an annual north-south migration of the Intertropical Convergence resulting in wet and dry seasons. Along tropical Eastern Pacific continental margins structural coral reefs are best developed in the Gulf of Chiriqui off western Panama. These reefs are relatively small, with reef formation taking place at a maximum depth of roughly 10 m. All of the reefs are judged to have formed since sea level approached its present height some 5,000 years ago. A study of the physical environment in the Gulf of Chiriqui revealed the following. Seasonal differences in surface temperatures were small but significant (P≅0.01), with the dry-season median (Md) of 28.9°C higher than the rainy season one of 28.0°C. At all times, surface-water temperatures were within the range considered optimal for coral growth. There were also significant (P<0.05) seasonal differences in the depths of the 25°, 20°, and 18°C isotherms. The first was shallowest (Md=18.5 m) during the rainy season due to vertical mixing, while the latter two were shallowest (Mds=31.5 and 33.0 m, respectively) during the dry season due to a generalized shoaling of the thermocline. All three isotherms are closely associated with the thermocline and showed remarkable variability in depth, most likely connected with internal waves. Salinities were reduced down to depths greater than 20 m and for distances of more than 50 km from the coast. Seasonal differences were slight (0.7% S) but statistically significant (P<0.01). Turbidity during the rainy season reduces the amount of light reaching the bottom at 10 m depth roughly by a factor of three compared to the dry season. Even the dry season amount is only about one half as much as would be expected to reach the same depth on the seaward reef of a Westen Pacific atoll. These conditions of cool water a short distance below the surface, reduced salinities, and high seasonal turbidity combine to make the region a poor one for coral-reef formation. The history of the Eastern Pacific coral fauna is traced from the Cretaceous to the Holocene. The present fauna is of Indo-Western Pacific origin, having become established following (1) the final closure of the connections between the Caribbean and Eastern Pacific (Pliocene), (2) movement of the northern Line Islands by sea-floor spreading into the path of the North Pacific Equatorial Countercurrent (Pliocene), and (3) the loss of all Eastern Pacific hermatypes during the Pleistocene.

Regulation of algal community development in a Macrocystis pyrifera forest

Abstract: The effects of small and large-scale roughness, overstory development, competition for space with sessile animals, and grazing on algal community development in a subtidal Macrocystis pyrifera forest were examined using specially prepared concrete blocks as substrata. Variation in small-scale roughness (crevices and grooves in the order of 0.1 to 3 mm width and depth) had no significant effects on community composition. However, M. pyrifera colonization, algal diversity, and sessile animal biomass were higher near the upper horizontal edges of blocks and concrete prisms. This “edge” effect may result from a combination of increased spore and larval settlement and enhanced growth of plants and animals associated with the turbulent eddies formed around these obstructions. Natural and experimentally produced variations in the algal overstory demonstrated that the presence of an overstory can reduce algal diversity and cover beneath. Caging experiments suggest that predatory fishes and sea-stars indirectly affect the algal community by removing sessile animals (primarily bryozoans) which compete with the algae for space. The exclusion of grazers resulted in increased growth of Gigartina spp. Selective grazing on this genus may account for its reduced abundance in the study area.

Further studies on decomposition of dissolved organic matter in coastal seawater

Abstract: Experiments were made on decomposition of dissolved organic matter (DOM) in coastal seawater (Sagami Bay and Tokyo Bay, Japan). Decomposition of DOM seems to proceed in two steps: a rapid decrease in DOM during the first several days, followed by a slow decrease after this time. The apparent rate constant for decomposition of the total DOM was calculated as 0.01 to 0.09 day-1 for the first step and 0.001 to 0.009 day-1 for the second step, assuming that such decomposition proceeds as a first-order reaction. A part of such utilizable fractions of DOM may be derived from excretion and decomposition products of phytoplankton, especially “red-tide” organisms occurring in summer. Molecular weight distribution of DOM changed with advancing decomposition. The low-molecular-weight DOM (mainly less than 500) in the surface water of Tokyo Bay was 0.67 mgC/l (24% of the total DOM) at the initiation of incubation; this decreased to 0.36 mgC/l (16% of the total DOM) after 2 days incubation at 20°C in the dark. Low-molecular-weight DOM was thought to be firstly utilized by micro-organisms. After 6 to 10 months incubation, the proportion of low-molecular-weight DOM decreased and that of high-molecular-weight DOM increased.

Synergistic effects of salinity, temperature and heavy metals on mortality and osmoregulation in marine and estuarine isopods (Crustacea)

Abstract: The effects of cadmium (3CdSO4·8H2O), zinc (ZnSO4·7H2O) and lead [Pb (NO3)2] on mortality, and cadmium, zinc and mercury (HgCl2) on osmoregulation, have been recorded for marine and estuarine species of isopods (Crustacea). The marine species studied were Idotea baltica, I. neglecta, I. emarginata and Eurydice pulchra, which were adapted to 100, 80, 60 and 40% sea water (SW) (100% SW э 34‰ S). The estuarine species used were Jaera albifrons sensu stricto and J. nordmanni, which were adapted to 100, 50, 10 and 1% SW. Both groups of isopods have low mortalities in 100% SW with 10 and 20 ppm of cadmium, zinc and lead, but a decrease in salinity caused an increase in the toxicities of these metals and reduced the LT50 values (time, in hours, to 50% mortality). Mortalities at 10°C were generally higher than those recorded at 5°C. Cadmium had no significant effect on the osmoregulation of I. baltica and I. emarginata in 100 and 80% SW at 5°C, but this metal significantly lowered the blood osmotic concentration of I. neglecta in 80% SW. Zinc did not alter the haemolymph osmotic concentration of I. neglecta in 100 and 80% SW, but significantly lowered the blood osmotic concentration of I. baltica in 100% SW. Cadmium, zinc and mercury also significantly altered the osmoregulatory ability of J. albifrons in dilute saline.

Environmental grain and polychaete species' diversity in a bathyal benthic community

Abstract: Patterns of polychaete species' dispersion in the San Diego Trough, Southern California Continental Borderland, North Pacific Ocean, at a depth of 1230 m are analyzed Samples consist of 4 replicate 025-m2 box cores, each partitioned into twenty-five 001-m2 subcores, and of 1 unpartitioned core The sampler is biased but, when this bias is taken into account, few species show strong aggregation either between or within cores If all species are considered together as replicates, intraspecific aggregation is detected between cores, but uniform dispersion dominates within cores Patchiness or habitat partitioning on the assayed scales can thus account for little of the extremely high species' diversity observed Apparently due to an environmental structure having a “grain” smaller than 001-m2, the diversity of species assumed to be sedentary is higher than the diversity of species assumed to be mobile One evidence of such structure is a negative covariance between paraonid abundance and density of “mudballs” constructed by a cirratulid Consideration of these results suggests that either grain specialization or simultaneous, biogenic disequilibrium or both act on spatial scales smaller than 001-m2 to maintain high polychaete species' diversity in the San Diego Trough

Selectivity in feeding by the deposit-feeding bivalve Macoma nasuta

Abstract: Macoma nasuta Conrad is primarily a deposit-feeding bivalve sucking the top millimeter of the sediment surface. Growth experiments show that surface sediment supports growth better than detritus falling from the water column. Gut clearance time is between 1 and 9 h (12°C). Fecal pellets are ejected in a regular rhythm. However, the total amount of feces per unit time shows considerable individual variation. Due to sorting in the mantle cavity, about 97% (dry weight) of the surface material is ejected again as pseudofeces. Selectivity by the bivalve is estimated by comparison of particle size and organic composition of sandy and muddy sediments and compared with feces produced by clams fed these sediments. Fecal pellets are in all cases richer in organic components than the sediment, indicating a high degree of selectivity. Ingestion and digestion of small animals (meiofauna) occur, but many of the ingested specimens survive. It is not possible to estimate the assimilation of organic matter by simple difference between the ingested sediment and the ejected feces. The difficulties in calculating energy budgets which arise from selective feeding and associated bacteria are discussed.

Reproduction, growth and photosynthesis of gametophytes of Laminaria saccharina grown in blue and red light.

Abstract: The induction of reproductive activity by blue light in female gametophytes of the brown alga Lamnaria saccharina has been investigated and related to other effects of red and blue light on these plants. Although germination of zoo-spores is slightly delayed in red light, female gametophytes grow at similar rates in blue and red light of the same quantum irradiance up to an age of 8 to 10 days, when plants in blue light begin to form eggs. The percentage of plants forming eggs is proportional to the total quanta of blue wavelengths received up to a saturating value of about 400 μE·cm-2; a 50% response is induced by 200 μE·cm-2. The action spectrum for the induction of fertility has a main peak at 430 to 450 nm, with two subsidiary peaks in the blue and one in the near-ultraviolet light, but the action spectrum for photosynthesis is quite different, with peaks in the red, green and blue regions. These results indicate that egg formation in female gametophytes occurs as a specific morphogenetic response to blue light, which is independent of photosynthesis and growth, and trial experiments with male gametophytes of L. saccharina and gametophytes of other species of Laminariales indicate that these plants react similarly.

Growth and reproductive cycles of the marine fouling ascidians Ciona intestinalis, Styela plicata, Botrylloides violaceus, and Leptoclinum mitsukurii at Aburatsubo-Moroiso Inlet (central Japan)

Abstract: Experimental cultivations of post-metamorphosis juveniles were repeated in different seasons for Ciona intestinalis (L.) and Styela plicata (Lesueur) (simple ascidians) as well as for Leptolinum mitsukurii (Oka) and Botrylloides violaceus Oka (compound ascidians) at Aburatsubo-Moroiso Inlet near Misaki Biological Station (Japan). Growth in body length of simple ascidians was exponential during juvenile development up to near sexual maturity. C. intestinalis grew to sexual maturity in 1 month in summer and in 2 months in winter; S. plicata, in 2 months in summer and in nearly 5 months in winter. The doubling time decreased approximately twofold in the two simple ascidians with a 10C° increase in environmental temperature. Growth of colonies in compound ascidians was exponential after maturation of the first functional zooids. Sexual reproduction of L. mitsukurii and B. violaceus was continuous throughout the year, forming many generations in a year. Doubling time of colony growth in the two compound ascidians decreased approximately threefold with a 10C° increase in temperature.

Abundance, breeding and growth of the crab Scylla serrata in two South African estuaries

Abstract: Populations of the crab Scylla serrata (Forskal) were studied in two South African estuaries from 1971 until 1974. One estuary was open to the sea, the other was closed by a sandbar. Population density in the closed estuary was estimated by means of mark-release-recapture data from tagged crabs. The population of S. serrata was estimated as 1 crab/124m2 and the production at 3.4 g/m2/annum. Catch per unit effort data from the closed estuary indicated a natural mortality of 41% in the crabs' second year and 60% in the third. Growth was studied in both estuaries by means of size-frequency analysis and from tagging returns. Growth was rapid in the first 12 to 15 months, when the crabs attained a carapace width of 80 to 160 mm. Thereafter growth slowed, and after 3 years crabs were between 140 and 180 mm in carapace width. Females mated in summer at a carapace width of 103 to 148 mm, males at 141 to 166 mm. After mating, females migrated out of both estuaries into the sea.

Nitrate uptake in marine phytoplankton: Energy sources and the interaction with carbon fixation

Abstract: Field studies of whole natural phytoplankton communities from Knight Inlet, B. C., Canada and laboratory cultures of the diatom Skeletonema costatum indicate inorganic carbon fixation may be temporarily suppressed following 10 to 15% enrichment with NO 3 - or NH 4 + . (This effect is suggested to be due to competition between inorganic carbon and nitrogen for adenosine triphosphate (ATP), and is reduced when chlorophyll a is increased intracellularly after 6 to 8 h.) Results imply that the source of ATP for nitrate uptake is primarily from Photosystem I (cyclic photophosphorylation) in the presence of light. It would appear that a transient nutrient-adaptive response occurs upon addition of extracellular nitrogen.

Partitioning of nitrogen and carbon in cultures of the marine diatom Thalassiosira fluviatilis supplied with nitrate, ammonium, or urea

Abstract: Small or negligible differences in growth rates, average cell size, yields in cell numbers and total cell volumes were found in cultures of Thalassiosira fluviatilis inriched with nitrate, ammonium, or urea. Intracellular pools of unassimilated nitrate, nitrate, and ammonium were found in nutrient-rich conditions, but urea was not accumlated internally. Nitrogen assimilation into organic combination rather than nitrogen nutrient uptake was a critical rate-limiting step in nitrogen utilization. The free amino acid pool, protein, lipid-associated nitrogen, pigments, and total cell nitrogen were all highest in young or mature phase cells and decreased with age in senescent cells, whereas chitan, lipid, carbohydrate, and total cellular carbon all continued to increase during senescence. Dissolved organic nitrogen compounds accumulated in the medium only during senescence. C:N and lipid:protein were sensitive indicators of nitrogen depletion and age in T. fluviatilis.

Ecology of Conus on eastern Indian Ocean fringing reefs: Diversity of species and resource utilization

Abstract: The most diverse assemblages of the genus Conus known occur on fringing coral reefs in Thailand and Indonesia. As many as 27 congeneric species of these gastropods inhabit a single reef; in all, we examined 1,350 individuals of 48 species. Several attributes of the populations we observed conform to expectations of a model of ecological characteristics of bench and reef Conus proposed by Kohn (1971a). Number of species (S) averaged 15, and species diversity (H″) averaged 2.3 in the most heterogeneous habitat type — topographically complex, subtidal reef platforms (Type III habitat). Both species richness and evenness of distribution of individuals among species contribute strongly to H″. Fewer congeners and greater numerical dominance by single species characterize more homogeneous habitats. On subtidal reef platforms with large areas of sand substrate and less coral limestone (Type I–III habitat), mean values were S=10, and H″=1.6. In the one intensively studied, truncated reef-limestone platform (Type II–III intermediate habitat), S=13 and H″=1.4. Summed population density of all Conus species in Type III and I–III habitats is similar (0.02 to 0.05 individuals /m2) and comparable to estimates from similar habitats elsewhere in the Indo-West Pacific region. Mean density (0.7/m2) and other population attributes in Type II–III habitat more closely resemble those of Type II than Type III habitats in general. We combined analysis of species diversity and other attributes of assemblages in habitats of different environmental complexity with analysis of microhabitat and food-resource utilization, in order to demonstrate the extent to which specialization on different resources occurs in assemblages differing in diversity and habitat type. In the habitats studied, co-occurring species of Conus specialized to a greater extent on different prey species than on different microhabitat patches, but degree of microhabitat specialization was greater than in similarly complex habitats with assemblages of lower diversity elsewhere in the Indo-West Pacific region. While most Conus species preyed primarily on a different species or higher taxon of polychaetes, diets are not more specialized or dissimilar than in similar habitats elsewhere. Degree of specialization on different prey is not correlated with Conus species diversity in the different types of habitats studied. The data lead to the conclusion that differential predation is as important — and differential microhabitat utilization is more important — in permitting coexistence of potentially competing congeners, compared with conditions in habitats of comparable heterogeneity that support fewer congeners farther from the center of the Indo-West Pacific region. Pairwise comparisons of congeners indicate that many species pairs have low or no overlap in both microhabitat and food utilization. Members of species pairs with high overlap in microhabitat utilization typically eat different prey organisms, and those with similar diets typically occupy different habitats or microhabitats. This applies to molluscivorous as well as vermivorous species. Information on the diets of 11 species is reported here for the first time. Of 48 Indo-West Pacific Conus species whose food is now known, 35 prey on polychaetes, 2 on enteropneusts, 6 on gastropods, and 5 on fishes. Vermivorous Conus prey on relatively few of the polychaete species present in the environments. Species eaten represent only 12% of a total estimated polychaete population density of 27,000 individuals /m2. Certain very abundant polychaetes may be protected from predation by Conus by their small size, others by their long tubes. Two new aspects of size-selective predation by Conus are reported: (1) Although comparisons of predation rate with prey standing-crop suggest that food is plentiful, selective predation on the largest prey individuals present suggests that only small proportions of prey-species populations may have large enough body size to repay foraging effort by the Conus present; (2) composition of the diet changes qualitatively with increase in body size in several vermivorous Conus species; shifting by larger individuals to larger prey species could be documented in C. ebraeus.

Grazing rates of the Atlantic menhaden Brevoortia tyrannus as a function of particle size and concentration

Abstract: The feeding behavior of adult Atlantic menhaden (Brevoortia tyrannus) upon 5 species of phytoplankton and 2 species of zooplankton has been studied. Four recognizable feeding stages which were a function of the concentration and size of the food particles were observed. During rapid feeding the fish swam at a constant speed for a prolonged period over a wide range of particle concentrations. Particle and food carbon-concentrations at the threshold for initiation and termination of feeding were inversely related to particle size. Carteria chuii (13.2 μ) was not grazed at a significant rate, while two-cell chains of Skeletonema costatum (16. 5 μ) were filtered from the water, indicating a minimum-size threshold for filtration of between 13 and 16 μ. The most rapid filtering rates were observed for the copepod Acartia tonsa (\(\bar x\) volume swept clear = 24.8 l/fish/min). The maximum food-particle size acceptable to a menhaden appears to be between Acartia tonsa (1200 μ) and adult Artemia salina (10 mm). These results suggest that the large schools of menhaden found in Atlantic coastal waters could have a significant effect on the plankton, selectively grazing zooplankton, larger phytoplankton, and the longer chains of chain-forming diatoms.

Excess allozyme homozygosity and breeding population structure in the Mussel Mytilus californianus

Abstract: Genetic variability and the distribution of this variability was examined in two size classes (1 to 2 mm and 9 to 10 cm valves) of the mussel Mytilus californianus. Marked homozygote excess was observed at two polymorphic loci (Lap and Pgi), and the excess was far greater in juveniles than in adults. It is suggested that both the homozygote excess and the significantly greater excess in juveniles are due to subdivision in the reproductive population.