Use of tidal freshwater marshes by fishes and macrofaunal crustaceans along a marsh stream-order gradient

Fishes and invertebrate macrofauna (nekton) were sampled biweekly (July through October 1985) from the surface of tidal freshwater marshes. Samples were collected with flume nets at three different stream orders (orders 2, 3 and 4+) along a marsh stream order gradient. Twenty-five species of fishes (5,610 individuals, 17.072 kg preserved wet weight) representing 13 families, and three species of invertebrates (19,570 individuals, 13.026 kg preserved wet weight) were collected. The most abundant species were grass shrimp (Palaemonetes pugio), mummichogs (Fundulus heteroclitus), banded killifish (F. diaphanus), inland silversides (Menidia beryllina), and blue crabs (Callinectes sapidus). Invertebrate catches (mostly grass shrimp and blue crabs) were not significantly different among stations. Total numbers of fishes were significantly greater at both headwater (order 2) and main creek (order 3) stations than river (order 4+) stations, but catches of headwater and main creek stations were not significantly different. The relationship between marsh stream order and fish abundance may partly be related to the distribution of submerged aquatic vegetation (SAV) within marsh tidal creeks. Submerged aquatic vegetation decreases in abundance with increasing stream order. Some species may use SAV as a refuge from predators or as a foraging area during low tide when the marsh surface is inaccessible. The presence of SAV in tidal creeks may enhance the habitat value of adjacent marshes.     

Catchability coefficients for coastal fishes caught in 366-meter and 732-meter long trammel nets struck with noise and rotenone

Catchability coefficients (q) of 366-m and 732-m trammel nets set along the shore in a rectangular shape were determined for selected fish species, utilizing noise and sublethal rotenone strike methods. Catachbility coefficients ranged from 0 to 1 for both trammel nets; 65% and 75% of the values for the 366-m and 732-m nets, respectively, were less than 0.1. Only the perpendicular strike method may have affected the catch efficiency of the nets, but the effect was not consistent among all species. Catchability coefficients were slightly higher when fish too small to be caught in the net were removed from the calculations. Despite the wide range of catchability coefficients among species, trammel nets struck with noise can be used to detect gross changes in abundance (standing stock) of many estuarine fishes. Increases in trammel net efficiency may be obtained by improvement in striking techniques or changes in net design, such as use of less visible monofilament webbing.     

Time series of the abundance of the post-larvae of the crabsCancer magister andcancer spp. on the Southern Oregon coast and their cross-shelf transport

Using stationary zooplankton nets that fished the tidal current we measured the daily abundance ofCancer crab megalopae near the mouth of Coos Bay, Oregon, during the 1997 spring settlement season. During the spring of 1997, the coastal waters were dominated by a significant El Niño event. Sea surface temperatures (SST) were higher than normal, upwelling indices were an order of magnitude smaller than during the two previous springs, and upwelling favorable winds were weak. Daily catches ofCancer magister megalopae ranged from 0 to 78 with 61% of the total catch occurring during four pulses. Peak catches tended to occur every 13.6 d close to 13.8 d average period between spring tides. Significant cross correlations were found between the maximum daily tidal range and the catch ofC. magister megalopae; large catches tended to occur 4 to 7 d after the spring tide. Daily catches ofCancer oregonensis andCancer productus ranged from 0 to 307 with catch significantly positively cross correlated to the maximum daily tidal range at a lag of ?5 days suggesting that the largest catches tended to occur after the spring tides. We hypothesize that a tidally-generated phenomenon internal waves, transportedCancer megalopae shoreward and caused the observed variation in their abundance in Coos Bay.     

Immigration of larvae of fall/winter spawning marine fishes into a North Carolina estuary

Larval fishes were sampled weekly from late fall to early spring in the Newport River estuary just inside Beaufort Inlet, North Carolina. Quantitative samples were taken during darkness at mid-flood tide with paired 60-cm bongo nets (505-μm mesh). Larvae of 22 species from 15 families were collected. Seventy-seven percent of the species and 97% of the individuals were fishes that had been spawned on the continental shelf and had immigrated to the estuary. In descending order, the five most abundant species, accounting for 90% of the individuals, were spot (Leiostomus xanthurus), Atlantic croaker (Micropogonias undulatus), Atlantic menhaden (Brevoortia tyrannus), pinfish (Lagodon rhomboides), and speckled worm ell (Myrophis punctatus). Most species immigrated through-out the winter and into spring, but there were distinct patterns in their temporal abundances.     

Collection efficiency of seine and rotenone samples from tidal creeks,cape fear river,North Carolina

Efficiency, defined as the percentage of the total number of individuals captured from a known area of tidal creek (blocked with seines), was studied on six occasions from December 1976 through August 1978. Sampling was conducted at two stations near the Cape Fear River, Southport, North Carolina using either seines or rotenone. For the three most abundant species collected by each method, the range for seine efficiencies (60.6±19.4 to 78.0±9.4%) was generally narrower than that for rotenone (29.6±9.5 to 57.7±14.8%). However, overall species richness was better represented by rotenone, the mean percentage of species captured for all samples was 92.1% versus 70.3% for seines. Consistent patterns in efficiency for individual species with regard to size, age, or water temperature were absent. A comparison of individual collections with that of the sample “universe” trapped between the block nets indicated that a representative sample of the extant nekton community was taken by each method.     

The cyclopoid copepods,Hemicyclops adhaerens andSaphirella sp., in the Damariscotta River estuary,maine, with a note to their possible relationship

During the 14-month collection period,Hemicyclops always appeared as naupliar stages andSaphirella as immature copepodite stages at 3 stations in the middle and lower estuary.Hemicyclops nauplii were abundant during late spring and summer, with a seasonal maximum of 7448/m³ in late spring at the upstream station.Saphirella stages were observed throughout the year, but higher population densities generally occurred in the summer and fall; the highest density was 3413/m³. Both species were usually more abundant upstream than downstream. The larvae may be life stages of a single bottom-dwelling species,Hemicyclops adhaerens.     

Resurgence of submersed aquatic macrophytes in the tidal Potomac River,Maryland, Virginia,and the District of Columbia

A 1978–81 survey of submersed aquatic macrophytes in the tidal Potomac River showed that there were virtually no plants in the freshwater tidal river between Chain Bridge and Quantico, Virginia, decades after the disappearance of plants in the late 1930’s. Plant populations were monitored in subsequent years (1983–85) using qualitative shoreline surveys and quantitative resampling of the original 1978–81 transects. In 1983, 12 species of submersed aquatic macrophytes were found in the tidal river. Population increases were dramatic; by fall 1985, plants had colonized all shallow areas between Alexandria and Gunston Cove, Virginia.Hydrilla verticillata dominated in Dyke Marsh-Hunting Creek and Swan Creek. Most other areas contained a variable mixture ofHeteranthera dubia, Myriophyllum spicatum, Ceratophyllum demersum, Vallisneria americana, Najas guadalupensis andHydrilla verticillata. No plants were found along the main river or in tidal embayments in the reach between Gunston Cove and Quantico, Virginia. Total dry weight collected in the upper tidal river in fall 1985 was 14.5 times that of spring 1985, and four times that of fall 1984.     

The distribution of shallow water juvenile fishes in an urban estuary: The effects of manmade structures in the lower Hudson River

The objective of this study was to determine what effect, if any, large pile-supported platforms (piers) have on the habitat distribution and abundance of juvenile fishes. Trapping techniques were used in 1993 and 1994 under piers, in pile fields, and in open-water habitat types in shallow areas (<5 m) in the lower Hudson River estuary (40°44′N, 70°01′W). Nearly 1500 fishes, mostly juveniles, representing 24 species were collected in 1865 trap-days from May through October in the 2-yr study. The presence of relatively large numbers of young-of-the-year (YOY) fish during both years lends support to the idea that shallow areas in the lower Hudson River estuary currently function as nursery habitats for a variety of fishes. Two seasonal assemblages were apparent, but their composition varied somewhat between years.Microgadus tomcod andPseudopleuronectes americanus YOY dominated an early summer assemblage (May–July) while large numbers of YOYMorone saxatilis were collected as part of a late summer assemblage (August–September). The effects of habitat type on fish assemblage structure were significant during both years. Fish abundance and species richness were typically low under piers; YOY fishes were rare andAnguilla rostrata accounted for a large proportion of the total catch. In contrast, YOY fishes dominated collections at pile field and open-water stations, where abundance and species richness were high. These results indicate that habitat quality under the platforms of large piers (>20,000 m²) is probably poor for YOY fishes when compared with nearby pile field and open-water habitat types.     

Effects of Local Shoreline and Subestuary Watershed Condition on Waterbird Community Integrity: Influences of Geospatial Scale and Season in the Chesapeake Bay

In many coastal regions throughout the world, there is increasing pressure to harden shorelines to protect human infrastructures against sea level rise, storm surge, and erosion. This study examines waterbird community integrity in relation to shoreline hardening and land use characteristics at three geospatial scales: (1) the shoreline scale characterized by seven shoreline types: bulkhead, riprap, developed, natural marsh, Phragmites-dominated marsh, sandy beach, and forest; (2) the local subestuary landscape scale including land up to 500 m inland of the shoreline; and (3) the watershed scale >500 m from the shoreline. From 2010 to 2014, we conducted waterbird surveys along the shoreline and open water within 21 subestuaries throughout the Chesapeake Bay during two seasons to encompass post-breeding shorebirds and colonial waterbirds in late summer and migrating and wintering waterfowl in late fall. We employed an Index of Waterbird Community Integrity (IWCI) derived from mean abundance of individual waterbird species and scores of six key species attributes describing each species’ sensitivity to human disturbance, and then used this index to characterize communities in each subestuary and season. IWCI scores ranged from 14.3 to 19.7. Multivariate regression model selection showed that the local shoreline scale had the strongest influence on IWCI scores. At this scale, percent coverage of bulkhead and Phragmites along shorelines were the strongest predictors of IWCI, both with negative relationships. Recursive partitioning revealed that when subestuary shoreline coverage exceeded thresholds of approximately 5% Phragmites or 8% bulkhead, IWCI scores decreased. Our results indicate that development at the shoreline scale has an important effect on waterbird community integrity, and that shoreline hardening and invasive Phragmites each have a negative effect on waterbirds using subestuarine systems.     

Late Cretaceous seasonal palaeoclimatology and diatom palaeoecology from laminated sediments

Laminated diatom-rich marine sediments from California and the Arctic Ocean provide a window into the seasonal climate and oceanography of the mid- and high-latitude Late Cretaceous. These remarkable shallow-buried sediments constitute palaeo-sediment traps that record exceptionally well-preserved sequential biogenic and lithogenic flux events. Many of the diatom laminae are composed of a few dominant taxa, and we use a species-based approach for palaeoecological interpretation. Contrary to many earlier interpretations, results indicate that both sites preserve a major flux of taxa adapted to exploit a strongly stratified ocean. The uppermost Maastrichtian Marca Shale of California records a seasonal cycle initiated with a spring bloom flux of diatom resting spores followed by a summer lithogenic sediment input likely driven by monsoonal storms providing river runoff and aeolian input. This is followed by a dominant diatom flux of species that thrived in the summer stratification in deep chlorophyll maxima and were sedimented in the fall when this stratification broke down. Dominant taxa comprising this group include Hemiaulus, Stephanopyxis, Stellarima and Rhizosolenia. The uppermost Campanian CESAR 6 core from the Arctic Alpha Ridge, records a spring bloom flux of resting spores followed by a more dominant summer and fall flux of diatom vegetative cells which were likely concentrated in subsurface summer blooms that generated a “summer export pulse” and by the breakdown of stratification in the fall that gave massive flux of deep chlorophyll maxima species in the fall dump. The dominance and diversity of Hemiaulus in the CESAR 6 core together with widespread evidence of N₂-fixation may indicate that some diatom blooms were powered by intracellular N₂-fixing cyanobacteria as in the modern oligotrophic ocean. Thin lenses of fine lithogenic sediment that occur mostly in the spring layer represent rafting by winter sea ice and support other evidence that suggests intermittent winter freezing in the Late Cretaceous Arctic.     

Seasonal succession and breeding cycles of three species of Acartia (Copepoda: Calanoida) in a maine estuary

Seasonal succession of three species of Acartia in a Maine estuary was examined. The well-defined successional pattern, in which A. tonsa is replaced, by A. clausi in winter and early spring, is well-documented in the middle Atlantic estuaries, but was not observed in this northern New England estuary. Instead, both species increased in their abundance at the same time on most occasions. In general, A. clausi was present throughout the year and produced three generations from March to November. A. longiremis had two or three generations between May and November, and disappeared during late summer. A. tonsa was present from May through December and was most abundant in early fall. A. clausi and A. tonsa were generally most numerous upstream, and A. longiremis downstream. Adult and copepodite V sex ratios varied among species, stations, and seasons. Seasonal patterns of Acartia populations in estuaries of the north Atlantic coast and their possible relationships to environmental factors were also compared and discussed.     

Sediment characteristics and molluscan fossils of the Farasan Islands shorelines,southern Red Sea,Saudi Arabia

The Farasan Islands are located about 40 km offshore of Jizan area, southern Red Sea, Saudi Arabia. This is a preliminary study aiming to collect shoreline sediments from 17 stations to describe their main lithologic characters and identify the dominant molluscs that could help to evaluate the environmental conditions of these islands. Also, a sediment core FARA2 was collected from the intertidal area of Khor As Sailah Lagoon to see the development of shoreline sediments in this area with time. The results indicated that the shoreline sediments of the Farasan Islands comprised mainly of white, biogenic sand enriched in remains of corals, molluscs, calcareous algae, and benthic foraminifera. Thirty-four mollusc species were recorded from these sediments. Among them, Strombus fasciatus, Strombus tricornis, Chicoreus ramosus, Chicoreus virgineus, Tridacna maxima, and Tridacna squamosa were the most common molluscan in/near the shoreline sediments of Farasan Islands. Frequency abundances of sediment grain-size fractions in the core FARA2 indicated that the shoreline of the Khor As Sailah Lagoon is developing towards shallow intertidal setting due to high production of biogenic sediments by reefal communities. Metal concentrations (Fe, Mn, Cu, and Zn) in the sediment of the core FARA2 were stable throughout, showing no remarkable changes. This finding could indicate that flux of detrital components by fresh water runoff or wind-blown dust over the Farasan Islands was un-detectable during the deposition of these sediments.     

Impact of Armored Shorelines on Shore-Zone Fish Density in a Mid-Atlantic,USA, Estuary: Modulation by Hypoxia and Temperature

Anthropogenic modifications of estuarine environments, including shoreline hardening and corresponding alteration of water quality, are accelerating worldwide as human population increases in coastal regions. Estuarine fish species inhabiting temperate ecosystems are adapted to extreme variations in environmental conditions including water temperature, salinity, and dissolved oxygen across seasonal, daily, and hourly time scales. The present research utilized quantitative sampling to examine the spatiotemporal distribution of shore-zone estuarine fish species in association with four unique shoreline types across a range of water temperature and dissolved oxygen conditions. Fish were collected from the intertidal and shallow subtidal region of four shoreline types, Spartina alterniflora marsh, Phragmites australis marsh, riprap, and bulkhead, in the summer and fall of 2009 and 2010. Analyses were performed to (1) compare mean fish density among shoreline types across all water conditions and (2) explore relationships of the complete fish assemblage, three functional species groupings, and two fish species (Fundulus heteroclitus and Menidia menidia) to unique shoreline/water conditions. Significantly greater mean fish densities were found along S. alterniflora shorelines than armored shorelines. Several metrics including fish density, species richness, and occurrence rates suggest S. alterniflora shorelines may serve as a form of refuge habitat during periods of low dissolved oxygen and high temperatures for various species, particularly littoral-demersal species including F. heteroclitus. Potential mechanisms that could contribute to a habitat providing refuge during adverse water quality conditions include tempering of the adverse condition (decreased temperatures, increased dissolved oxygen), predation protection, and increased foraging opportunities.     

Predation on soft-shell clams,Mya arenaria,by the common mummichog,Fundulus heteroclitus

Invertebrate predation has been cited as the major factor determining post-settling survival of the soft-shell clam, Mya arenaria. Feeding studies on common mummichogs, Fundulus heteroclitus, in Essex Bay, Massachusetts, from July 1976 to June 1978 showed soft-shell clams to be an important diet item in fish greater than 55 mm TL. Biweekly quantitative seining from 16 April to 24 September 1977 revealed predation peaks in the spring and fall corresponding to March–April and June–July spawning periods for M. arenaria. In spring and fall 1977 and spring 1978, 38.5% of the male and 52.8% of the female mummichogs sampled over 55 mm TL averaged 6.77 and 7.32 clams per stomach respectively. The maximum number of clams per stomach was 49 (108 mm female), and 47 (100 mm male). Quantitative seining at low tide yielded mummichog densities from 0.35 to 6.04 fish/m². Combining mummichog density estimates with soft-shell clam predation data gave a possible consumption of 546,000 M. arenaria per km low tide shoreline per day during peak predation periods. Results indicate mummichog predation may equal or exceed invertebrate predation as a major cause of small (<12 mm) soft-shell clam mortality in the Gulf of Maine.     

The annual cycle of zooplankton in a Long Island estuary

Zooplankton and chlorophyll-a samples and associated hydrographic data were collected at approximately weekly intervals in the Peconic Bay estuary for most of the period between May 1978 and June 1979. Surface zooplankton samples were obtained by simultaneously-towed 73 μm- and 202 μm-mesh nets, and subsurface samples were collected with 505 μm-mesh nets. Zooplankton numbers and displacement volumes fluctuated widely throughout the year, with highest values in early spring and summer. Juvenile or adult copepods accounted for means of 90.0% and 85.0% of the animals recorded for the 202 μm- and 73 μm-net samples, respectively. The combination of Acartia tonsa and A. hudsonica adults+copepodids accounted for a mean of 81.4% of the zooplankton recorded for the 202 μm-net samples, and the combination of copepod nauplii, Acartia spp. adults+copepodids, Oithona colcarva and Parvocalanus crassirostris accounted for a mean of 82.7% of the animals recorded for the 73 μm-net samples. Copepod nauplii were the most abundant zooplankters collected in the 73 μm-net samples, and they were generally collected in higher numbers than the total number of animals in the 202 μm-net samples. During the colder months, late copepodids and adults of larger copepod species comprised greater proportions of the total zooplankton than during the warmer months when nauplii and copepodids of smaller copepod species were predominant. The ctenophore Mnemiopsis leidyi and the medusa Cyanea capillata also had periods of abundance during warmer months. Differences between numbers of larger zooplankters collected over different depth intervals or in successive replicate tows over the same depth intervals, reveal the likely effects of both vertical and horizontal patchiness. Comparisons of zooplankton numbers from the present investigation, which were obtained with relatively fine-mesh nets, with values from previous studies in adjacent waters which used coarser-mesh nets, suggest that many previous investigations have seriously underestimated the numbers of smaller zooplankters, particularly copepod nauplii.     

Egg Deposition by Atlantic Silverside, Menidia menidia: Substrate Utilization and Comparison of Natural and Altered Shoreline Type

Egg deposition by the intertidal spawning fish Atlantic silverside (Menidia menidia) was compared among six shoreline types (Spartina alterniflora, Phragmites australis, sandy beach, riprap, riprap-sill, and bulkhead) and various substrates. In spring 2010, M. menidia egg density was measured daily near Roosevelt Inlet, Delaware Bay, USA. Over 3,000,000 eggs were collected during 50 sampling days. Eggs were deposited at all six shoreline types, with >93?% of eggs collected from S. alterniflora shorelines. Choice of substrate for egg attachment was similar across shoreline types with >91?% of eggs collected from filaments of the green alga Enteromorpha spp., a disproportionately high utilization rate in comparison with Enteromorpha spp.'s relative coverage. This study demonstrates that S. alterniflora shoreline, in association with Enteromorpha spp., is the preferred spawning habitat for M. menidia and that hardened shorelines and shorelines inhabited by P. australis support substantially reduced egg densities.     

Distribution and characterization of luminescent bacteria in a temperate estuary

The effect of temperature and salinity on numbers of luminescent bacteria present in waters of the Mystic (Conn.) River estuary was evaluated. Counts decreased with decreasing salinity; none were detected at freshwater stations. A population maximum of 35 per ml was noted at the highest salinity station (30±2‰). Highest counts were observed during winter and spring and lowest numbers occurred during summer and fall months. Isolates (111) were identified and compared with previously-described luminescent bacteria; i.e.,Beneckea (Vibrio) harveyi, Photobacterium (V.) fischeri, P. phosphoreum, andP. leiognathi. All species were isolated but distinct seasonal differences were noted.P. (V.) fischeri andB. (V.) harveyi represented 93% of the luminous population on an annual basis. Only the former was found during the period December through March (highest count 7 per ml) whileB. (V.) harveyi was the dominant species noted between May and October (maximum count 11 per ml).P. leiognathi andP. phosphoreum were found only during July and August as 7% of the total luminous population. All isolates grew at NaCl concentrations between 6 and 30‰; none grew below 6‰     

The value of salt marsh edge vs interior as a habitat for fish and decapod crustaceans in a Louisiana tidal marsh

Flume nets of various lengths and a 3-m seine were used to sample the fishes and macrocrustaceans using a flooded Louisiana salt marsh and the adjacent tidal creek. The experiment allowed for species-specific comparisons of the flooded marsh at the creek edge versus the interior. Of the 37,667 organisms collected in flume nets from January through November 1989, 89% were decapods (nine species) and 11% were fish (29 species). An additional 18,539 organisms (75% decapods and 25% fish) were collected from concurrent seine samples taken from July through November. Comparison of catches among different flume lengths and low tide versus high tide seine collections revealed distinct patterns of marsh habitat utilization. Densities of most organisms were highest within 3 m of the water’s edge, but significant numbers of marsh-resident fish species used the interior marshes. The edge marshes appeared to be used by both transient and resident species; however, the interior marshes were used primarily by marsh-resident species (Cyprinodontiformes andPalaemonetes sp.) that are excellent food sources for adult transient-species. Four zonations of marsh use are described for transients, residents, and rare species.     

Seagrass die-off in Florida Bay: Long-term trends in abundance and growth of turtle grass,Thalassia testudinum

Beginning in late 1987 Florida Bay experienced a large and unprecedented die-off ofThalassia testudinum. The die-off occurred only in stands of denseT. testudinum. We initiated an experimental monitoring effort in 1989 to attempt to ascertain the cause of this die-off phenomenon. From 1989 to 1995 the abundance and productivity ofT. testudinum was measured at five stations associated with the seagrass die-off and three stations where no die-off had occurred (including one on the seaside of Key Largo, outside of Florida Bay). Early in the study the salinity was very high, exceeding 46 psu, but it has decreased to 29–38 psu in recent years. Seagrass standing crop and either short-shoot density or mass per short shoot declined at nearly all stations, including the stations without die-off (unaffected stations). Over the course of the study, areal productivity declined at three die-off stations; but mass-specific productivity increased at all die-off stations and one unaffected station. Seasonality was pronounced; detrended standardized residuals showed responses for all of the seagrass parameters to be greater than the yearly mean in spring and summer and less than the mean in fall and winter. Detrended residuals also showed decreased productivity to be correlated with increased salinities in the summer despite a long-term record of declining salinities. We propose a conceptual model of the seagrass die-off phenomenon. We document that salinity does contribute to stress onT. testudinum in Florida Bay, but salinity is believed to be only one contributing factor to the loss of seagrasses. The documented increase in the mass-specific productivity ofT. testudinum over the period 1989–1995 suggests seagrasses are growing rapidly in Florida Bay by 1995; we predict that the loss ofT. testudinum may be slowing down and that recovery is possible.     

Oyster Predation by Black Drum Varies Spatially and Seasonally

Oyster reefs (Crassostrea virginica) supply important ecosystem services to estuarine habitats in the northern Gulf of Mexico, but little is known of the role of fish predators in controlling their structure or areal cover on soft sediments. At two sites and during fall and spring, we employed gill nets and trot lines to remove black drum (Pogonias cromis) from experimental reefs, and assessed oyster survival in comparison to control reefs. Numbers and biomass of black drum removed from reefs varied seasonally, among sites, and among removal methods. In the fall, black drum were rare at one site and abundant at the other, but did not significantly lower oyster survival on control reefs at either site. In the spring, black drum were common at both sites, and significantly lowered oyster survival on control reefs. Oysters and epizoic hooked mussels comprised roughly a third of the fishes’ diet, and oyster mortality was closely related to the percentage of drum feeding on oysters. There was little evidence of mortality from other predators of seed oysters like stone crabs or Southern oyster drills, and a repeated measures analysis of variance indicated black drum biomass was significantly depressed on experimental reefs during the experiments. Black drum thus appear to be potentially important predators on oyster reefs, but more work needs to be done on what factors explain the temporal and spatial variation in their abundance and oyster consumption.