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At least 235 records · Page 13Linked to original sources
USGS1990

Influence of seasonal growth, age, and environmental exposure on Cu and Ag in a bivalve indicator, Macoma balthica, in San Francisco Bay

Temporal and spatial variations in Cu and Ag in the deposit-feeding clam Macoma balthica and in surficial sediments were analysed at 8 stations in San Francisco Bay at near-monthly intervals for periods ranging from 3 to 10 yr during 1977 to 1986. Strong seasonal variations in metal concentrations of M. balthica were associated with seasonal variations in soft tissue weight. Aperiodic fluctuations in metal concentration appeared to be driven by changes in metal content of the soft tissues. Metal content of clams of standard shell length was less variable than tissue metal concentration, and generally followed changes in the concentrations of Cu and Ag in the sediments. Correlations between metal content and sediment concentrations were improved when content was standardized to age rather than shell length. Metal content of M. balthica displayed few consistent temporal trends among stations, evidently reflecting different sources of input and complex hydrologic and geochemical processes affecting metal availability in San Francisco Bay. Increases in Cu and Ag were noted at several stations in South Bay during 1977 to 1980. A continuous 10 yr record at one of these stations showed that the 1977 to 1980 increase and the subsequent decline beginning in 1981 coincided with fluctuations in metal inputs from a nearby source.

California↗
USGS1990

Remarkable invasion of San Francisco Bay (California, USA), by the Asian clam Potamocorbula amurensis. I. Introduction and dispersal

The euryhaline bivalve mollusc Potamocorbula amurensis (family Corbulidae), a native of China, Japan, and Korea, has recently appeared and become very abundant in San Francisco Bay. This clam appears to have been introduced as veliger larvae in the seawater ballast of cargo vessels. It was first collected in northern San Francisco Bay in late 1986. P, amurensis then spread throughout the estuary within 2 yr and reached densities at some sites exceeding 10 000 m -2 It lives primarily in the subtidal on all substrates (mud, sand, peat, and clay) and is found in the full range of bay salinities (< 1 to 33%). Its explosive increase in abundance and spread may result in major alterations of the San Francisco Bay estuary ecosystem. These could include changes in (1) trophic dynamics (through competition with other suspension-feeding and deposit-feeding infauna; changes in benthic community energy flow; availability of a new and abundant prey item for birds, fish, and crabs; and reduction - as a result of its filter feeding - of phytoplankton standmg stock) and (2) benthic dynamics (through inhibition and/or enhancement of infauna due to substrate destabilization; alteration of suspended sediment load of near-bottom water; and change of sediment surface redox balance). The early detection of the appearance and spread of P. amurensis in San Francisco Bay makes this one of the best documented invasions of any estuary in the world.

California↗
USGS1982

Does the benthos control phytoplankton biomass in South San Francisco Bay?

South San Francisco Bay, USA, is a shallow coastal embayment that receives large inputs of nutrients (N. P, Si) and small local inputs of freshwater. Phytoplankton dynamics are typically characterized by a spring bloom when surface chlorophyll a increases from < 5 to > 40 mg m -3 . The bloom persists for 2 to 4 wk, and then dissipates. Phytoplankton biomass remains low (chlorophyll a < 5 mg m -3 ) from May through December, although light and nutrient availability are sufficient to sustain growth rates of 1 to 1.5 divisions d -1 in the expansive shallows. Transport processes apparently exert a small influence on phytoplankton biomass, and calculated zooplankton grazing accounts for only a small reduction in net rate of phytoplankton population growth in the shallows. However, suspension-feeding bivalves are sufficiently abundant to filter a volume equivalent to the volume of South Bay at least once daily. These observations suggest that grazing by benthos is the primary mechanism controlling phytoplankton biomass during summer and fall.

California↗
USGS1988

Effects of food deprivation on the larvae of two flatfishes

For greatest survival, first-feeding halibut Paralichthys californicus and diamond turbot Hypsopsetta guttulata required food by the day of total yolk absorption. Some halibut larvae survived if fed 1 or 2 d after yolk depletion, but their growth rate was significantly less than larvae fed earlier. Survival of 3-wk-old larvae was greater in treatments with shorter starvation periods. A small percentage of 3-wk-old halibut larvae recovered from a maximum starvation period of 4 d while 3-wk-old diamond turbot successfully resumed feeding any time during food deprivation intervals lasting up to 9 d. Longer periods of starvation resulted in significant morphological differences – diamond turbot starved longer were not only smaller, but also less developed. In the field, larvae may experience varying periods of food deprivation due to differing spatial and temporal prey patch distributions. Our results demonstrate that differences in starvation resistance, and possibly mortality under patchy feeding conditions, are ontogenetic and species-specific.

Marine Ecology Progress Series↗
USGS1991

Time-courses in the retention of food material in the bivalves Potamocorbula amurensis and Macoma balthica significance to the absorption of carbon and chromium

Time courses for ingestion, retention and release via feces of microbial food was investigated using 2 bivalves with different feeding strategies, Potamocorbula amurensis and Macoma balthica . The results showed 2 pathways for the uptake of food material in these clams. The first is represented by an initial label pulse in the feces. The second pathway operates over longer time periods. Inert 51 Cr-labeled beads were used to determine time frames for these pathways. The first pathway, involving extracellular digestion and intestinal uptake, is relatively inefficient in the digestion of bacterial cells by P. amurensis but more efficient in M. balthica . The second pathway, involving intracellular digestion within the digestive gland of both clams, was highly efficient in absorbing bacterial carbon, and was responsible for most chromium uptake. Differences in the overall retention of microbial 51 Cr and 14 C relate not to gut-passage times but to the processing and release strategies of the food material by these 2 clams.

Marine Ecology Progress Series↗
USGS1985

Effect of adherent bacteria and bacterial extracellular polymers upon assimilation by Macoma balthica of sediment-bound Cd, Zn and Ag

Effects of adherent bacteria and bacterial extracellular polymer (exopolymer) upon uptake of particle-bound Cd, Zn and Ag by the deposit-feeding clam Macoma balthica were studied in the laboratory. Amorphous iron oxyhydroxide and unaltered and alkaline-extracted sediments were used as model particulates in separate, controlled deposit-feeding experiments. In general, amounts of metal taken up from ingested particles varied dramatically with the nature of the particle surface. Ingestion of contaminated iron oxide particles did not contribute to overall uptake of Cd and Ag in feeding clams, but accounted for 89 to 99% of total Zn uptake. Exopolymer adsorbed on iron oxide particles caused an increase in the biological availability of particle-bound metals in the order Ag>Cd>Zn, whereas adherent bacteria up to 3.2 X 10 11 g -1 had no effect upon amounts of metal taken up from ingested particulates. At the higher Cd and Ag concentrations employed (3.6 X 10 -7 M), feeding rates declined with increasing amounts of iron oxide-bound exopolymer, suggesting behavioral avoidance due to increased metal availability. Much of the Cd (57 %) taken up by clams feeding on unaltered estuarine sediments originated from particulates, even though particle/solute distribution of Cd (86%) was similar to that in experiments with iron oxide particles. Uptake of Cd from alkalineextracted sediments was insignificant, as it was from unamended iron oxide. However, addition of exopolymer (10 mgg -1 sediment) caused a restoration nn bioavailability of sediment-bound Cd.

Marine Ecology Progress Series↗
USGS1985

Persistence of an introduced mud flat community in south San Francisco Bay, California

The benthic invertebrate community inhabiting the extensive and sedimentologically homogeneous mudflats of South San Francisco Bay has demonstrated a high degree of constancy in both species composition and relative abundance among species throughout 10 yr of observation. The community, composed predominantly of introduced species with opportunistic lifestyles, is dominated numerically by Gemma gernma , Ampelisca abdita , and Streblospio benedicti . The key to the persistent co-occurrence of these species on the mudflats seems to lie in the combination of (1) the recurrence of minor disturbances of the mudflat habitat (e.g. sediment deposition/erosion, inundation by low-salinity water) on time scales comparable to that of life cycles; (2) opportunistic life history strategies (rapid maturity, brooding of young, multiple generations each year, ease of local dispersal of both juveniles and adults) that permit continued colonization of the mudflat surface or rapid recolonization after disturbances. Only 1 of the 3 numerically-dominant species. A. abdita , displays an annual periodicity in abundance. S. benedicti and G. gemma , through broadly flexible reproductive strategies permitted in the mild San Francisco climate, can exhibit strong recruitment at any time between spring and autumn. The most extreme community changes, involving temporary reduction or elimination of normally dominant populations, occurred as a result of anomalous disturbances such as unusual buildup and decay of an algal mat during 1 summer and prolonged periods of unusually high freshwater inflow during 2 successive winters. The introduced opportunists routinely co-occur at high densities. However, one of these, the tube-dwelling amphipod A. abdita , may control the abundance of the native mollusk Macoma balthica .

Marine Ecology Progress Series↗
USGS1990

Remarkable invasion of San Francisco Bay (California, USA) by the Asian clam Potamocorbula amurensis . II. Displacement of a former community

Long-term macrobenthic sampling at a site in northern San Francisco Bay has provided an unusual opportunity for documenting the time course of an invasion by a recently introduced Asian clam Potamocorbula arnurensis . Between 1977, when sampling began, and 1986, when the new clam was first discovered, the benthic community varied predictably in response to river inflow. During years of normal or high river inflow, the community consisted of a few brackish or freshwater species. During prolonged periods of low river inflow, the number of species doubled as estuarine species (e.g. Mya arenana ) migrated up the estuary. In June 1987, at the beginning of the longest dry period in recent decades, large numbers (> 12 000 m -2 ) of juvenile P. arnurensis were discovered at the site. By midsummer 1988 the new clam predominated (> 95 %) in both total number of individuals and biomass, and the expected dry-period estuarine species did not become re-established. The rapid rise of P. arnurensis to numerical dominance throughout the region of the original introduction was probably facilitated by the fact that this region of the bay had been rendered nearly depauperate by a major flood in early 1986. Once introduced, the clam had sufficient time (> 1 yr) to become well established before the salinity regime was appropriate for the return of the estuarine species. Subsequently, the new clam was apparently able to prevent the return of the dry-period community. Its ability to live in low salinity water (< 1 %o) suggests that P. amurensis may not be displaced with the return of normal winter river flow and, therefore, may have permanently changed benthic community dynamics in this region of San Francisco Bay.

Marine Ecology Progress Series↗
USGS1986

Scale-dependent correlation of seabirds with schooling fish in a coastal ecosystem

The distribution of piscivorous seabirds relative to schooling fish was investigated by repeated censusing of 2 intersecting transects in the Avalon Channel, which carries the Labrador Current southward along the east coast of Newfoundland. Murres (primarily common murres Uria aalge ), Atlantic puffins Fratercula arctica , and schooling fish (primarily capelin Mallotus villosus ) were highly aggregated at spatial scales ranging from 0.25 to 15 km. Patchiness of murres, puffins and schooling fish was scale-dependent, as indicated by significantly higher variance-to-mean ratios at large measurement distances than at the minimum distance, 0.25 km. Patch scale of puffins ranged from 2.5 to 15 km, of murres from 3 to 8.75 km, and of schooling fish from 1.25 to 15 km. Patch scale of birds and schooling fish was similar m 6 out of 9 comparisons. Correlation between seabirds and schooling birds was significant at the minimum measurement distance in 6 out of 12 comparisons. Correlation was scale-dependent, as indicated by significantly higher coefficients at large measurement distances than at the minimum distance. Tracking scale, as indicated by the maximum significant correlation between birds and schooling fish, ranged from 2 to 6 km. Our analysis showed that extended aggregations of seabirds are associated with extended aggregations of schooling fish and that correlation of these marine carnivores with their prey is scale-dependent.

Newfoundland↗
USGS1987

An empirical model for estimating phytoplankton productivity in estuaries

e have previously shown that primary productivity in San Francisco Bay, USA, is highly correlated with phytoplankton biomass B (chlorophyll a concentration) and an index of light avallability in the photic zone, 2, I, (photic depth times surface irradiance). To test the generality of this relation, we compiled data from San Francisco Bay and 5 other USA estuarine systems (Neuse and South Rivers, Puget Sound, Delaware Bay and Hudson River Plume), and regressed daily produclvity J' P (mg C m-2 d-') against the composite parameter B Z, I,. Regressions for each estuary were significant and typically over 80 % of the varialon in P was correlated with variations in B Z,I,. Moreover, the pooled data (n = 211) from 4 estuaries where methodologies were comparable fell along one regression line (r2= 0.82), indicating that primary productivity can be estimated in a diversity of estuarine waters from simple measures of phytoplankton biomass and hght availability. This implies that physiological variabhty (e. g. responses to variations in nutrient availabhty, temperature, sahnity, photoperiod) is a secondary control on phytoplankton production in nutrient-rich estuaries, and that one empirical function can be used to estimate seasonal variations in productivity or to map productivity along estuarine gradients of phytoplankton biomass and turbidity.

Marine Ecology Progress Series↗
USGS1984

Significance of biomass and light availability to phytoplankton productivity in San Francisco Bay

Primary productivity was measured monthly at 6 sites within San Francisco Bay, USA, throughout 1980. The 6 sites were chosen to represent a range of estuarine environments with respect to salinity, phytoplankton community composition, turbidity, and water depth. Annual net production over the photic zone ranged from 95 to 150 g C m-2, and was highest in regions of lowest turbidity. Daily photic zone net productivity PN,, ranged from 0.05 to 2.2 g C m-2 d-', and was significantly correlated with the composite parameter B I,/& (where B = phytoplankton biomass; I, = daily surface insolation; E = attenuation coefficient). Lnear regression of PN,, against B Io/€ indicated that most (82 %) of the spatio-temporal variability in primary productivity within this estuary is explained by variations in light availability and phytoplankton biomass. We also calculated annual water-column net productivity PN, as a fraction of annual gross productivity PGx The ratio PN,, : PG, was inversely related to the ratio of water depth H to annual mean photic depth Z,. This linear relation indicates that the watercolumn of San Francisco Bay is a net photosynthetic source of organic carbon only when the ratio H : Z, < 6. In deep turbid habitats, where H : Tp > 6, respiratory loss exceeds productivity. Thus, 2 empirical formulations allow us to estimate productivity over the photic zone and water column from simple properties that are easily measured.

California↗
USGS2019

Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem

Major ecological realignments are already occurring in response to climate change. To be successful, conservation strategies now need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species-level diversity. As part of an effort to provide such information, we conducted a climate vulnerability assessment that included all Pacific salmon and steelhead (Oncorhynchus spp.) listed under the U.S. Endangered Species Act. Using an expert-based scoring system, we ranked 20 attributes for the 28 listed units, and 5 additional units. Attributes captured biological sensitivity, or the strength of linkages between each listing unit and the present climate; climate exposure, or the magnitude of projected change in local environmental conditions; and adaptive capacity, or the ability to modify phenotypes to cope with new climatic conditions. Each listing unit was then assigned one of four vulnerability categories.

California↗
USGS2017

Host-dependent differences in resource use associated with Anilocra spp. parasitism in two coral reef fishes, as revealed by stable carbon and nitrogen isotope analyses

The role of parasites in trophic ecology is poorly understood in marine ecosystems. Stable isotope analyses (SIA) have been widely used in studies of trophic ecology, but have rarely been applied to study the role of parasites. Considering that some parasites are associated with altered host foraging patterns, SIA can help elucidate whether parasitism influences host trophic interactions. French grunt ( Haemulon flavolineatum ), an abundant Caribbean coral reef fish, contributes greatly to trophic connectivity. They typically depart the reef at dusk, feed overnight in seagrass beds, and return to the reef at dawn. The large parasitic isopod Anilocra haemuli commonly infects French grunt, and infected fish are less likely to complete their diel migration, and are in poorer condition than uninfected conspecifics. Brown chromis ( Chromis multilineata ) are diurnally feeding planktivores and infection by Anilocra chromis does not influence host condition. To determine if Anilocra infection influences host diet and foraging locality, we conducted stable carbon and nitrogen isotope analyses on scale, muscle, heart and gill tissues of infected and uninfected French grunt and brown chromis. We determined that all French grunt had δ 13 C values representative of seagrass habitats, but infected French grunt were significantly enriched in 13 C and 15 N compared to uninfected conspecifics. This suggests that compared to uninfected conspecifics, infected French grunt forage in seagrass, but on isotopically enriched prey, and/or are in poorer condition, which can elevate δ 13 C and δ 15 N values. For brown chromis, infection did not significantly influence any δ 13 C and δ 15 N values; hence they all foraged in the same environment and on similar prey. This is the first study to use SIA to examine differences in resource use by Caribbean coral reef fishes associated with parasitism and to evaluate how closely related parasites might have host-dependent effects on host trophic ecology.

Marine Ecology↗
USGS2004

Seafloor habitat mapping and classification in Glacier Bay, Alaska: Phase 1 & 2 1996-2004

Glacier Bay is a diverse fjord ecosystem with multiple sills, numerous tidewater glaciers and a highly complex oceanographic system. The Bay was completely glaciated prior to the 1700’s and subsequently experienced the fastest glacial retreat recorded in historical times. Currently, some of the highest sedimentation rates ever observed occur in the Bay, along with rapid uplift (up to 2.5 cm/year) due to a combination of plate tectonics and isostatic rebound. Glacier Bay is the second deepest fjord in Alaska, with depths over 500 meters. This variety of physical processes and bathymetry creates many diverse habitats within a relatively small area (1,255 km 2 ). Habitat can be defined as the locality, including resources and environmental conditions, occupied by a species or population of organisms (Morrison et al 1992). Mapping and characterization of benthic habitat is crucial to an understanding of marine species and can serve a variety of purposes including: understanding species distributions and improving stock assessments, designing special management areas and marine protected areas, monitoring and protecting important habitats, and assessing habitat change due to natural or human impacts. In 1996, Congress recognized the importance of understanding benthic habitat for fisheries management by reauthorizing the Magnuson-Stevens Fishery Conservation and Management Act and amending it with the Sustainable Fisheries Act (SFA). This amendment emphasizes the importance of habitat protection to healthy fisheries and requires identification of essential fish habitat in management decisions. Recently, the National Park Service’s Ocean Stewardship Strategy identified the creation of benthic habitat maps and sediment maps as crucial components to complete basic ocean park resource inventories (Davis 2003). Glacier Bay National Park managers currently have very limited knowledge about the bathymetry, sediment types, and various marine habitats of ecological importance in the Park. Ocean floor bathymetry and sediment type are the building blocks of marine communities. Bottom type and shape affects the kinds of benthic communities that develop in a particular environment as well as the oceanographic conditions that communities are subject to. Accurate mapping of the ocean floor is essential for park manager’s understanding of existing marine communities and will be important in assessing human induced changes (e.g., vessel traffic and commercial fishing), biological change (e.g., rapid sea otter recolonization), and geological processes of change (e.g., deglaciation). Information on animal-habitat relationships, particularly within a marine reserve framework, will be valuable to agencies making decisions about critical habitats, marine reserve design, as well as fishery management. Identification and mapping of benthic habitat provides National Park Service mangers with tools to increase the effectiveness of resource management. The primary objective of this project is to investigate the geological characteristics of the biological habitats of halibut, Dungeness crab, king crab, and Tanner crab within Glacier Bay National Park. Additionally, habitat classification of shallow water regions of Glacier Bay will provide crucial information on the relationship between benthic habitat features and the abundance of benthic prey items for a variety of marine predators, including sea ducks, the rapidly increasing population of sea otters, and other marine mammals.

Alaska↗
USGS2021

Can identifying discrete behavioral groups with individual-based acoustic telemetry advance the understanding of fish distribution patterns?

Identifying patterns of organismal distribution can provide valuable insights for basic and applied marine and coastal ecology because understanding where animals are located is foundational to both research and science-based conservation. Understanding variation in distributional patterns can lead to a better assessment of ecological drivers and an improved ability to predict consequences of natural and altered relationships. Here, our purpose is to explore if quantifying coexisting groups of individual fish predators advances our understanding of field distribution patterns. Toward this end, we quantified locations of 59 acoustically tagged striped bass ( Morone saxatilis) within a 26-stationary unit telemetry receiver array in Plum Island Estuary (PIE), MA, United States. We then used cluster analyses on spatial and temporal-spatial metrics from this dataset to (1) assess if distinct groups of individuals coexisted, (2) quantify group characteristics, and (3) test associations between groups and distribution (e.g., physical site type and region). Based on multiple lines of evidence, we identified four groups of striped bass with different space use patterns that persisted across seasons (summer and fall). Similar-sized striped bass clustered at spatial and temporal scales at which individuals within distinct groups could, and did, physically overlap. In addition, distributional groups were linked to components of physical site type and region suggesting that discrete groups of individuals can interact differently with the environment within the same ecological system. The identification of these distinct groups of individuals creates a baseline from which to explore further ecological implications of grouping behavior for research and conservation in geographically large, temporally dynamic, and spatially heterogeneous marine and coastal environments.

Massachusetts↗
USGS2022

Estimating Pacific walrus abundance and survival with multievent mark-recapture models

Arctic marine ecosystems are undergoing rapid physical and biological change associated with climate warming and loss of sea ice. Sea ice loss will impact many species through altered spatial and temporal availability of resources. In the Bering and Chukchi Seas, the Pacific walrus Odobenus rosmarus divergens is one species that could be impacted by rapid environmental change, and thus, population assessments are needed to monitor changes in the status of this ecologically and culturally important marine mammal. We conducted a 5 yr genetic mark-recapture study to estimate demographic parameters for the Pacific walrus. We developed a Bayesian multievent mark-recapture model to estimate walrus survival and abundance while accounting for age misclassification. We estimated the probability of juvenile annual survival as 0.63 (95% credible interval [CrI]: 0.39-0.87) and adult female annual survival as 0.90 (95% CrI: 0.74-1.00). We estimated total abundance as 257 193 (95% CrI: 171 138-366 366). We provide the first estimate of total Pacific walrus abundance since an aerial survey in 2006, which generated a substantially less precise total population size estimate (129 000; 95% CI: 55 000-507 000). The emerging ecosystem state in the northern Bering and Chukchi Seas will likely result in a decline in Pacific walrus abundance, but there is substantial uncertainty regarding the magnitude of the anticipated decline. Our demographic estimates provide critical information to evaluate future population trends of this subsistence resource vital to communities that border the Bering and Chukchi Seas in the USA and Russia.

Alaska↗