Abundance Of Amphipods Research Articles

Distribution of antarctic zooplankton around Elephant Island during the austral summers of 1988, 1989, and 1990

Year to year variation and vertical distributions of epipelagic Zooplankton around Elephant Island and King George Island were examined with samples collected with bongo nets and a 1 m2 MOCNESS during the austral summers (Jan–Feb.) of 1988, 1989 and 1990. Copepods were the major components of epipelagic Zooplankton (in numbers) with dominance of Metridia gerlachei (1988 and 1989) and small calanoids and cyclopoids (1990). Euphausiids and salps were the next most abundant groups. The percent composition of euphausiids decreased from 1988 to 1990 while that of salps increased. The abundance of salps exceeded euphausiids and major taxa of copepods in 1990. Local patches of polychaetes and amphipods were also found. Statistically significant annual variations with increased numbers in 1990 were found by analyses of variance in total abundance, abundances of copepods, salps, chaetognaths and amphipods, but abundances of euphausiids, polychaetes and fishes showed no significant annual variations. When the study area was divided geographically, horizontal variability in abundance within each year showed no significance in total abundance, abundances of copepods, euphausiids, amphipods and fishes, but significance in salps, polychaetes and chaetognaths. Results of site clustering based on covariances of abundances of eleven major taxa were well matched, though not perfect, with the distribution of surface water temperatures which could be used as a tracer of source water masses suggesting that spatial variation was related to hydrodynamic conditions. Factor analyses showed that annual and spatial variations in abundance were mainly caused by only two taxa, Metridia gerlachei and salps (mostly Salpa thompsoni). These two taxa were responsible for about 60% and 30% of total variance, respectively, and were useful indicators of the interannual variation. That is, 1988 and 1989 were the years of M. gerlachei, and 1990 was the year of salps. From vertically stratified MOCNESS samples, it was shown that the major taxa in this study area were active vertical migrators. While most samples obtained by relatively shallow tows (uppermost 100 m depth) were composed of exclusively one or two taxa, those from relatively deep tows (down to 200 m) showed various patterns of vertical stratification suggesting that the patterns of vertical migration were species specific. Species specific ontogenetic vertical migration associated with elevated habitat temperatures also seemed to be responsible for the annual variation in zooplankton distribution in the upper water column.

EFFECT OF ROCKY INTERTIDAL AMPHIPODS ON ALGAL RECRUITMENT: A FIELD STUDY1

ABSTRACTEvidence about the potential of mobile marine invertebrates to act as algal spore dispersal agents is presently circumstantial. Using a field correlational and experimental protocol, our study tested the hypothesis that amphipods can increase the spore recruitment of the red algaIridaea laminarioidesBory.Iridaea laminarioidesspore recruitment onto glass slides was measured at a site with high amphipod abundance and a site with low density of amphipods. To evaluate the effect of anUlvacanopy on recruitment, replicated glass slides with and without a surroundingUlvacanopy were installed at both sites. The number ofI. laminarioidesspores recruited on the glass slides was four to eight times higher at the high amphipod abundance site than at the low density site. However, the presence of anUlvacanopy covering the glass slides did not significantly increase the recruitment ofI. laminarioides.Because the abundance ofI. laminarioides, the proportion of cystocarpic plants, and the percentage of open cystocarps only differed slightly between the low and high abundance amphipod sites, we suggest that the variation in recruitment between the sites is due to the differences in amphipod abundance (and their movements) and not to differences in spore production. Moreover, the presence ofI. laminarioidescystocarps showing amphipod grazing scars was significantly higher at the high amphipod density site than at the low density site.

Use of sequential sampling of amphipod abundance to classify the biotic integrity of acid-sensitive lakes

Use of sequential sampling of amphipod abundance to classify the biotic integrity of acid-sensitive lakes

Monitoring the shallow sublittoral using the fauna of kelp ( Ecklonia radiata) holdfasts

The macrofaunal community inhabiting the holdfast of the kelp, Ecklonia radiata, was assessed for changes along a putative gradient resulting from an outfall of low volume domestic effluent. Multi-dimensional scaling (MDS) revealed a consistent separation of treatment sites from controls at each of the three sample periods. Changes in trophic structure were dectected as well as shifts in relative abundances of amphipods and polychaetes as measured by the amphipod to polychaete ratio. Data were further analysed using the Ewens-Caswell neutral model which proved a useful tool for detecting differences between samples from control and treatment locations.

PERACARIDS ASSOCIATED WITH SABELLARIID WORM ROCK (PHRAGMATOPOMA LAPIDOSA KINBERG) AT SEBASTIAN INLET, FLORIDA, U.S.A.

ABSTRACT The amphipod and isopod crustaceans associated with colonies of the sabellariid worm Phragmatopoma lapidosa were sampled monthly from rock jetties at Sebastian Inlet, Florida, for 1 year. Six isopod and 10 amphipod species were collected. The isopods were strongly dominated by 2 species, Paradella dianae and Sphaeroma walkeri, which composed 98% of total isopod abundance. The amphipods were dominated by 3 species, Hyale perieri, Elasmopus pectinicrus, and Ampithoe pollex, which together made up 91% of total amphipod abundance. Densities of the dominant isopods showed 2 seasonal peaks, in early spring and in fall, associated with recruitment of small individuals to the habitat. Amphipod seasonal abundance patterns were species specific and generally less clear than for the dominant isopods. Maximum estimated abundances of both isopod species (35,000-50,000 m-2) and amphipod species (4,000-22,000 m-2) were high relative to maximum abundances recorded from other peracarid habitats in the region.

Do predatory fishes affect the structure of an epiphytal amphipod assemblage on a protected algal reef in Hawaii?

On a sheltered Hawaiian algal reef seaweeds are abundant and large herbivorous fishes are absent. Epiphytal amphipods are abundant on their seaweed habitats. Predator exclusion experiments were conducted to determine if predatory fishes affect the abundance, diversity, and size distribution of the epiphytal amphipod community living on plant substrata. Results suggested that amphipod abundance, expected number of species, and size distribution were all independent of predation pressure.

Patterns of abundance of exoedicerotid amphipods on sandy beaches near Sydney, Australia

Spatial and temporal patterns of abundance of two species of exoedicerotid amphipod at several sandy beaches near Sydney, Australia are described and related to physicochemical factors. Replicate cores were taken at monthly intervals for one year from the swash zone and data were analysed by two-way (site × month), fixed-factor analysis of variance. Spatial and temporal differences in abundance were usually significant but inconsistent because of significant site × month interactions. Spatial differences in Exoediceroides maculosus sometimes occurred in the absence of obvious corresponding physicochemical differences although the density of stranded seagrass and algae may affect abundance. The abundance of Exoediceros fossor was often greater in lagoons than open beaches. Salinity, temperature and storms had no apparent effect on the temporal patterns of abundance of either species.

Caprellid amphipods: fast food for the reproductively active

Caprellid amphipod abundance within seagrass meadows of Padilla Bay, Washington, USA, reaches >93 specimens · 625 cm −2 during winter. When shiner perch Cymatogaster aggregata Gibbon invade the seagrass on reproductive migrations, caprellid abundances drop to <2 specimens · 625 cm −2. Although caprellids normally do not constitute a major item in fish diets, shiner perch preferentially preyed upon the caprellids immediately following immigration into the grassbeds. This “critical window” of predation previously has not been reported.

The cryptofauna of Zostera marina (L.): Abundance, biomass and population dynamics

Cryptofauna (epifauna passing a 2-mm but retained on a 0.2-mm mesh sieve) of Zostera marina on the Swedish west coast (58°N, 11°E) is dominated by crustaceans, mainly detritivorous tube-building amphipods and harpacticoids. Abundance and biomass of amphipods in two relatively unpolluted Z. marina beds were higher than any data from the literature, with maximum abundance of 80·10 3 ind·m −2 and 1 g AFDW·m −2 bottom. This is at least partly due to the small mesh size used in this investigation. The recruitment of the crustaceans started in late June and was continuous through the rest of the season, whereas the recruitment of the molluscs peaked in late June and July. In a Z. marina bed (Rixö) located 2 km from an oil refinery, the seasonal abundance of amphipods was 15% of the abundance in the other beds, whereas the remaining fauna had about the same density. In Rixö the percentage of female amphipod with empty brood pouches increased during the season. It is suggested that low abundances and fecundity of amphipods in Rixö could result from oil pollution.

Does algal morphology affect amphipod susceptibility to fish predation?

This study evaluated the hypothesis that phytal amphipods are less susceptible to predation by fishes when on highly branched, morphologically complex algal hosts than when on seaweeds with a simple bladed morphology. Contrary to this hypothesis, laboratory experiments demonstrated that the amphipod Ampithoe longimana (Smith) was more susceptible to predation by the pinfish Lagodon rhomboides (L.) when on any of four highly branched seaweeds ( Hypnea musciformis (Wulf.) Lamouroux, H. comuta (Lamour.) J. Agardh, Gracilaria tikvahiae McLachlan, or G. verrucosa (Huds.) Papenruss) than when on either of two species with a simpler sheetlike morphology ( Padina gymnospora (Kutz.) Sonder or Ulva sp.) The morphologically intermediate alga Sargassum filipendula J. Agardh provided an intermediate level of protection. Similar experiments were conducted using plastic aquarium plants of highly branched and sheetlike morphology to evaluate the effects of host-plant morphology without the potentially confounding effects of other species-specific algal characteristics. The pattern evident in our tests with real plants was repeated in only one of two tests with plant mimics. This variable effect of host morphology combined with a demonstration that pinfish consumed the highly branched species Hypnea musciformis in preference to Padina gymnospora or Sargassum filipendula suggests that the susceptibility of phytal amphipods to predation by omnivorous fishes like Lagodon may be affected by both host-plant morphology and host-plant palatability to fishes. In field experiments the density of amphipods colonizing and surviving on Hypnea was significantly lower than their density on Padina or Sargassum regardless of whether the plants were protected from or exposed to fishes. In similar assays using only Sargassum, no clear effect offish predation on abundance of phytal amphipods could be demonstrated in the presence of high colonization rates by amphipods. Seasonal patterns of amphipod abundance on different host plants suggested that fish predation may be affecting the density of amphipods on Hypnea more than on Sargassum or Padina. In the summer, fish predation on amphipods becomes high. During this period, amphipod density per algal mass declined on Hypnea, slowly increased on Sargassum, and remained relatively constant on Padina. This field pattern of seasonal change in amphipod abundance as a function of algal host is consistent with our conclusion from laboratory studies that amphipods are more susceptible to omnivorous fish predation when on Hypnea, which is both morphologically complex and a high-preference food for the fish.

Composition and Seasonality of Sand-Beach Amphipod Assemblages of the East Coast of Florida

Sand-beach amphipods were sampled across an intertidal-subtidal gradient at several locations on the east central coast of Florida in 1982-1983 and 1985-1986. The amphipods collected represented 16 families and 40 species, although the Haustoriidae dominated (83%) total abundance. Five species, in order of abundance, Bathyporeia parkeri, Parahaustorius longimerus, Eudevenopus honduranus, Rhepoxynius epistomus, and Parahaustorius holmesi, made up 90% of total amphipod abundance. Only 1.5% of total amphipod abundance was found in the intertidal zone in this study, in marked contrast to other studies of sand-beach amphipods on the east coast of the United States. Abundance and species richness of amphipods increased sharply just below the swash zone. This spatial pattern is consistent with the hypothesis of Dahl (1953) that intertidal amphipods should become a less abundant component of the fauna on tropical beaches as compared to temperate ones. Strong seasonal patters of abundance and species richness are present, with lowest values in the winter months. This temporal pattern does not appear to correlate with predator activity.

The role of seaweed complexity in structuring Hawaiian epiphytal amphipod communities

Among Hawaiian marine algal species with different morphologies, seaweed complexity (surface area to biomass ratio) is not a consistent predictor of epiphytal amphipod abundance or number of species. Some seaweed species with relatively high complexity supported low numbers of amphipod individuals and species. Hawaiian epiphytal amphipods are not generally seaweed specific to certain seaweeds, rather they are distributed among many species. The results of this study show that the relationships between complexity of algae and the distribution and abundance of amphipods are neither simple nor direct.

Effects of nutrients and grazers on periphyton phosphorus in lake enclosures

SUMMARY. 1. Periphyton. measured as particulate phosphorus (PP) and expressed as periphyton PP, growing on vertically oriented substrata (polyvinyl impregnated nylon) under different nutrient loadings, light intensities (exposures), and grazer communities was examined in eight large enclosures (750 m3) where nutrients (N and P) and planktivorous fish (1+yellow perch) were added in a 2x2 factorial design.2. During the first 3 weeks of the experiment (25 June to 15 July), there was a significantly higher accumulation of phosphorus into periphyton (periphyton PP) with fertilization, but fish addition had no effect. During the fourth to seventh weeks (16 July to 12 August), addition of fish was associated with lower abundance of amphipods and chironomids and higher concentration of periphyton PP. In the enclosures without fish, these invertebrates were over 25 times more abundant, and periphyton PP decreased substantially compared to the June‐July period. Fertilization increased periphyton PP only at high exposures in the enclosures with fish.3. Exposure had a significant effect on periphyton PP. In the enclosures with fish, high abundance of nanoplankton reduced water transparency, and periphyton PP was lower in the deeper waters which may have been due to limitation by low light. Lower periphyton PP was also observed at the surface on sunny sides of enclosures without fish, and therefore with high water transparency. This pattern may have been due to inhibitory effects of high light intensity.4. Periphyton communities in the enclosures with fish had higher uptake rates for planktonic phosphorus, and lower rates of phosphorus release, suggesting that periphyton with high phosphorus demand may have high internal cycling of assimilated phosphorus.

Isoetid-zoobenthos associations in acid-sensitive lakes in Ontario, Canada

The macrophyte and associated epiphytic invertebrate community were quantitatively sampled within the littoral zones of 18 oligotrophic lakes in south-central Ontario. Densities for 7 of 10 benthic taxa were significantly greater within Eriocaulon septangulare With. dominated mats compared with clusters of Lobelia dortmanna L. overlying sand beach. The microdistribution and abundance of amphipods was dependent on, and significantly correlated with, isoetid biomass. The depth distribution of littoral invertebrates was also closely associated with the attenuation of macrophyte biomass. Estimates of mean annual biomass ranged from 91.5 to 475.3 g dry wt m −2 for Eriocaulon, and from 44.9 to 192.1 g dry wt m −2 for Lobelia. Biomass showed no trend in relation to lake pH within the range 5.6–6.7, nor to total phosphorus in water from 5 to 14 mg m −3. The previously-documented decrease in abundance of several littoral zoobenthic species in conjunction with lowered pH in Haliburton-Muskoka, Ontario lakes, seems explainable by direct H + toxicity in support of laboratory work, rather than through any secondary effect ascribed to disappearance of habitable substrate.

Estuarine Macrobenthos in Calcasieu Lake, Louisiana: Community and Trophic Structure

Macrobenthic assemblages in Calcasieu Lake estuary (Louisiana) were sampled at 11 sites from October 1983 through November 1985. The sites were numerically dominated by subsurface-deposit feeders, consisting mostly of polychaetes. Greater densities of macrofauna were collected at the northern (upper) stations of the lake than were collected in West Cove or the southern stations. Abundances of polychaetes, oligochaetes, and amphipods at the upper lake stations accounted for most of the differences among stations. The numerical dominance by detritivores (97% of the fauna) and lack of strong sediment or salinity gradients across the estuary, resulted in an absence of temporal pattern in trophic structure of the macrofauna.

Spatial and temporal distribution of Amphipoda associated with mussel beds from the Bay of Santos (Brazil)

Effects were determined of some abiotic factors on the patterns of abundance and diversity of amphipods associated with Perna perna (L.) beds. Observations were conducted at 2 sites subjected respectively to h g h and low degrees of wave exposure. The sampllng program combined the following 4 environmental aspectsseasonal effects, wave ac t~on , vertical zonation and tide level. Sixteen species were found, of which 7 occurred only at the exposed slte. The lowest values of density and number of species corresponded to the protected site; high values charactenzed samples from the exposed site. Jassa falcata dominated at the exposed s ~ t e but was absent at the protected mussel bed. The dominant species common to both stations were: Elasmopus brasiliens~s, E. pectenicrus and Hyale sp. 1. The distribution of arnphipods appeared to be a function of 3 main factors, as shown by correspondence analysis. structural heterogeneity of the mussel bed (related to wave action), verbcal zonation, and desiccation. Accordingly, cluster analysis pointed out wave action and zonation as the 2 key factors affecting similanty of samples. The cluster analysis of s p e c ~ e s showed few cases of high similarity and when so, the amph~pods differed In 11fe style. Thls niche partition partially explains coemstence of the amphipod assemblage in the mussel beds. Direct effects of wave impact seemed less important than its side effects (e.g. sedimentahon) as regards selection of specles, and t h ~ s was related to the physical protecbon of the mussel mats

Scavenging and other feeding habits of lysianassid amphipods (Orchomene spp.) from McMurdo Sound, Antarctica

The distribution and scavenging habits of the two most abundant lysianassid amphipods in McMurdo Sound differ markedly. Orchomene plebs lives primarily in deep water (>100 m), where planktonic and benthic food is sparser and scavenging events are less common and predictable than in shallower water. Orchomene plebs is common in shallow areas (<100 m) only under the Ross Ice Shelf and along the western McMurdo Sound. Here Weddell seals frequent tidal cracks in which they discard carrion and defecate; otherwise food is scarce. Orchomene pinguides lives on shallow (<10 m) wave-cut benches that are rich in food along the eastern McMurdo Sound. They, along with other omnivorous invertebrates which scavenge the food-rich eastern sound benches, are rare from shallow water along the western sound. The eastern benches are bathed by dense plankton blooms and harbor a high biomass of benthic diatoms and invertebrates. Scavenging events there were observed throughout the year. Orchomene plebs is larger and more motile, and came to laboratory carrion and baited field traps more rapidly and in greater numbers than O. pinguides. The crop contents of O. plebs contained only amorphous organic matter that suggested a scavenging habit. Crops of O. pinguides contained not only amorphous organic matter but also invertebrate prey, especially planktonic copepods that impact the bottom during winter.

Quantitative sampling of demersal zooplankton: reentry and airlift dredge sample comparisons

The distributions and abundances of demersal gammarid amphipods from a shallow sandy benthos were examined using core, reentry and airlift dredge sampling methods. Approximately 90% of the gammarid amphipods sampled with cores were found in the uppermost 2.5 cm of natural sediments. Reentry samplers, designed to contain sediments similar to natural sediments, were used in situ to sample demersal gammarids returning to the benthos after nocturnal vertical migrations. Airlift dredge samplers were used to estimate the absolute abundance of demersal gammarids within the benthos. Comparisons of reentry and airlift dredge samples indicated that only ≈11% of the gammarid fauna was actively migrating and recolonizing sediments during the night sampled. There were no differences between the relative orders of abundance of gammarid species sampled by reentry and airlift methods. Although reentry samplers may not be used to estimate absolute abundances of demersal organisms, they do estimate accurately the relative orders of abundance of demersal gammarid species. Therefore, reentry samplers may be used to test hypotheses regarding the effects of environmental variables upon the relative abundance, distribution, and sediment colonization behavior of demersal organisms.

Breakdown of Ficus fistulosa (Moraceae) leaves in Hong Kong, with special reference to dynamics of elements and the effects of invertebrate consumers

ABSTRACTSeasonal variations in the breakdown and dynamics of chemical elements in Ficus fistulosa leaves in a mixed forest on Hong Kong Island were investigated between October 1982 and September 1983. Mean rate of leaf material weight loss from coarse-mesh (3 mm) bags was 1.82% day-1, about four times that inside fine-mesh (0.2 mm) bags (mean rate 0.44% day-1). Breakdown rates varied seasonally with maximum rates in spring or summer, and were significantly correlated with prevailing temperatures, the rainfall of the two previous months, and the soil moisture content of the previous month. Potassium and Mg were rapidly leached from leaf material throughout the year while the concentrations of C, N, P, Ca and Na remained relatively stable. In the absence of macrofauna (inside fine-mesh bags) decomposition rate constants (k) were positively correlated with the mean abundance of mites and Collembola, as well as with total invertebrate abundance. In the presence of macrofauna (inside coarse-mesh bags) decomposition rate constants were positively correlated with isopod and amphipod abundance. There was no significant correlation between breakdown rates of leaf material and mesofaunal abundance inside coarse-mesh bags. The importance of climate and invertebrates as rate determinants of Ficus decomposition is discussed.

Secondary production of four sublittoral, soft-sediment amphipod populations in the Bay of Fundy

Estimates of secondary production by cohort summation of losses and size–frequency methods were made on the four most abundant amphipods at an 80 m deep station on a soft sediment in the southwestern mouth of the Bay of Fundy. Production and annual turnover ratios (production:biomass ratio (P:B), in parentheses) for the 1978 year class, expressed as grams wet preserved weight per square metre per year, were as follows: Haploops fundiensis, 0.505 (1.3); Photis reinhardi, 0.370 (2.8); Casco bigelowi, 1.210 (2.5); Harpinia propinqua 0.066 (3.1). The P:B ratios found were closest to those calculated by the empirical method of Robertson when an accurate estimate of life-span was available.