Benthic-slope fishes found at 900m depth along a transect in the western N. Atlantic Ocean

The species composition of the benthic-slope fish fauna of the Middle Atlantic Bight is described from trawl catches taken from a depth of about 900 m in August, 1969. Two species associations and an intermediate area are apparent. The difference between the two associations is partially attributable to differences in species composition, but primarily to a difference in species dominance. The small number of samples precludes geographic and bathymetric delineation of these associations, as well as conclusions about their temporal stability. Diversity values appear to be relatively high for the benthic fishes of the upper slope, but comparison with values for temperate estuaries and coastal fishes indicates a narrow range for all of these habitats, and considerable overlap in values from the different environments. Environmental stability may be of less importance in determining the diversity of fish faunas than of benthic invertebrate faunas because of the mobility of fishes and ontogenetic changes in their habitat preference.     

Stalked tunicates Boltenia ovifera form biogenic habitat in the rocky subtidal zone of Nova Scotia

The stalked tunicate Boltenia ovifera is widely distributed in the Arctic and North Atlantic oceans on rocky substrata at 10–300 m depth, although its ecological role in benthic communities is poorly understood. The distribution and abundance of B. ovifera were recorded at 10–100 m depth in towed-video transects in November 2011 and in June, July, and November 2012 off a wave-exposed headland near Halifax, Nova Scotia. Specimens also were collected at 30 m depth using SCUBA (44°26.88′N, 63°31.59′W) in September 2012. Areas dominated by B. ovifera had densities of 10–100 individuals m^?2 on rocky substrata at 30–60 m depth. These tunicate beds often were associated with sparse kelp (Agarum clathratum) and turf-forming red algae. A generalized additive model indicated that depth, substrate type, and benthic algal type were strong predictors of tunicate abundance. Twenty-two epibiotic species were found on specimens of B. ovifera, including juvenile conspecifics. Filter-feeding macroinvertebrates, including anemones and soft corals, were more abundant in areas with B. ovifera than in areas without these tunicates. Our findings suggest that beds of B. ovifera can act as biogenic habitat to enhance local species richness in the rocky subtidal zone of Nova Scotia.     

Spatial distribution patterns of the soft corals Alcyonium acaule and Alcyonium palmatum in coastal bottoms (Cap de Creus, northwestern Mediterranean Sea)

Current knowledge on the abundance and distribution patterns of different soft coral species is relatively limited when compared to other benthic suspension feeders such as gorgonians and hard coral species. To overcome this scarcity of information, the distribution patterns of the soft corals Alcyonium acaule and Alcyonium palmatum were investigated in northwestern Mediterranean benthic communities over a wide geographical (60 km of coastline) and bathymetrical (0–70 m depth) extent using a remotely operated vehicle. A. acaule was the most abundant species in the study area with highest recorded density of 18 col m^?2 found at depths of 35–45 m in areas that are directly exposed to strong near-bottom currents. Conversely, A. palmatum was only found as scattered solitary colonies at greater depths in soft bottoms, with maximum density of 2.4 col m^?2. Medium and large colonies of A. acaule were preferentially found on sloping and vertical rocky bottoms where they form dense patches. High-density patches of A. acaule were preferentially found on vertical rocky bottom, while isolated colonies were preferentially observed on coralligenous substrata as well as on flat soft and maërl substrates. A. acaule biomass distribution showed highest values between 40 and 45 m depth, and between 60 and 65 m depth. This suggests that deeper populations are formed by colonies that are bigger than the equivalent shallower ones. Although both species are almost genetically identical, ecologically they are very different. For this reason, conservation plans should consider the differential ecological traits shown by these two soft coral species.     

Benthic community respiration in the N.W. Atlantic Ocean: in situ measurements from 40 to 5200 m

Benthic community respiration was measured in situ at 9 stations along the Gay Head-Bermuda transect from depths of 40 to 5200 m. Three methods were used; bell jar respirometers, grab respirometers, and free vehicle respirometers. Benthic community respiration rates spanned three orders of magnitude, decreasing from 21.5 ml O₂ m^-2 h^-1 at 40 m in November to 0.02 ml O₂ m^-2 h^-1 at 5200 m. Rates decreased two orders of magnitude between 40 and 1800 m and then significantly declined again between the continental rise (3650 m) and the abyssal plain stations. Predictive equations for benthic community respiration along the transect reflect a strong correlation with depth of water. Of lesser significance are the correlations with water temperature, dissolved oxygen, benthic animal biomass, surface primary productivity and sediment organic matter. Calculations show that annual benthic respiration can utilize 1 to 2% of the surface primary productivity. Of the 2 to 7% organic carbon fixed at the surface which supposedly reaches the bottom, only 15 to 29% is utilized by the benthic community at 2200, 3000, and 3650 m. The energy requirements of other biological components of deep-sea benthic communities, such as benthopelagic and macro-epibenthic animals, not included in these measurements, must also be considered in calculating a balance of carbon.Contribution from Scripps Institution of Oceanography.     

Microphytobenthos of the Dogger Bank: a comparison between shallow and deep areas using phytopigment composition of the sediment

The surface sediment characteristics related to benthic microalgae primary production were studied at the Dogger Bank, North Sea, in order to evaluate the potential role of microphytobenthos as a food source for the macrobenthic fauna. Twenty-one stations were sampled in July 2001 and May 2002, with water depth ranging from 16.3 to 68.5 m. High-performance liquid chromatography pigment analyses revealed that concentrations of chlorophyll a, chlorophyll c and fucoxanthin are mainly associated with benthic diatom flora at most parts of the Dogger Bank. High percentage of phytopigments (>50%) was firmly attached to sand grains at the stations shallower than 40 m water depth. The deeper stations were characterized by a phytopigment composition originating from pelagic phytoplankton settled on the sea floor. Qualitative microscopy showed that the benthic microflora on top of the Bank mainly consists of small diatoms (5–10 μm), such as e.g., Diploneis spp., living attached to the sand grains. The results are discussed concerning possible implications for ecology and biogeochemistry of the Dogger Bank area.     

Benthic algal production across lake size gradients: interactions among morphometry, nutrients, and light

Attached algae play a minor role in conceptual and empirical models of lake ecosystem function but paradoxically form the energetic base of food webs that support a wide variety of fishes. To explore the apparent mismatch between perceived limits on contributions of periphyton to whole-lake primary production and its importance to consumers, we modeled the contribution of periphyton to whole-ecosystem primary production across lake size, shape, and nutrient gradients. The distribution of available benthic habitat for periphyton is influenced by the ratio of mean depth to maximum depth (DR = z/ z(max)). We modeled total phytoplankton production from water-column nutrient availability, z, and light. Periphyton production was a function of light-saturated photosynthesis (BPmax) and light availability at depth. The model demonstrated that depth ratio (DR) and light attenuation strongly determined the maximum possible contribution of benthic algae to lake production, and the benthic proportion of whole-lake primary production (BPf) declined with increasing nutrients. Shallow lakes (z < or =5 m) were insensitive to DR and were dominated by either benthic or pelagic primary productivity depending on trophic status. Moderately deep oligotrophic lakes had substantial contributions by benthic primary productivity at low depth ratios and when maximum benthic photosynthesis was moderate or high. Extremely large, deep lakes always had low fractional contributions of benthic primary production. An analysis of the world's largest lakes showed that the shapes of natural lakes shift increasingly toward lower depth ratios with increasing depth, maximizing the potential importance of littoral primary production in large-lake food webs. The repeatedly demonstrated importance of periphyton to lake food webs may reflect the combination of low depth ratios and high light penetration characteristic of large, oligotrophic lakes that in turn lead to substantial contributions of periphyton to autochthonous production.     

Morphological, physiological and reproductive conditions of rafting bull kelp (Durvillaea antarctica) in northern-central Chile (30°S)

The bull kelp Durvillaea antarctica is a common floating alga in the southern hemisphere, but despite the ecological and biogeographic importance of kelp rafts, little is known about the responses of detached kelps to the conditions at the sea surface. The morphological, physiological and reproductive performances of D. antarctica rafts in the Coastal System of Coquimbo, Chile (CSC, ~30°S), were examined during winter and summer of two successive years (2010/11 and 2011/12). Epibionts (Lepas spp.) that only attach to floating objects were used as indicator for the floating time of kelp rafts. Photosynthetic efficiency and reproductive maturity of both benthic and floating algae varied seasonally, with a stronger decrease in summer than in winter. Blade size (measured as weight proportion of kelp individuals), phlorotannin concentrations and antioxidant activities were lower in floating than in benthic algae. Environmental conditions and floating time affected the blade tissues, with stronger negative effects during summer. These results confirm that floating persistence of D. antarctica in the CSC is suppressed during the summer months, which indicates that the dispersal potential of this (and other) floating algae varies seasonally.     

青海尕海盐湖初级生产力特点

１９９７ 年夏季对青海尕海盐湖的生态系统进行了初步研究． 初级生产力研究结果表明：（１） 水域毛初级产氧量平均值为３ ．２７３ｇ ｍ －２ｄ－１ ,其中底栖藻类占７０．９９％ ,底栖藻类单位面积毛初级生产力是浮游植物的２．４５倍．（２） 水域初级生产力构成格局为：由沿岸到湖心区,随着水深的逐步增大,底栖藻类初级生产力逐步减少,浮游植物初级生产力逐渐占主导地位． 前者所占的比例在０．５５ ｍ 水深时为９７．７２ ％ ,在大于１３．０ ｍ 水深后即降至０．０ ％ ．（３）与国际有关文献相比,尕海盐湖初级生产力较低     

Relationship between depth, sediment, latitude, and the structure of benthic infaunal assemblages on the mainland shelf of southern California

A regional benthic survey was conducted in 1994, and the data were used to assess the relationship among three habitat factors (depth, sediment grain size, and latitude) and the distribution of benthic infaunal assemblages on the southern California coastal shelf. Benthic samples were collected with a 0.1 m² Van Veen grab from 251 sites on the continental shelf (10–200 m deep) from Point Conception, California, to the United States–Mexico international border. The relationship between habitat and assemblages was investigated by conducting a Q-mode cluster analysis to define groups of stations with similar species composition and then examining whether differences were present in physical habitat attributes among those groups of stations. Analysis of data from 175 uncontaminated sites yielded four habitat-related benthic infaunal assemblages along the southern California coastal shelf: a shallow-water assemblage from 10–32 m, a mid-depth assemblage between 32 and 115 m, and two deep-water (115–200 m) assemblages, one in fine and one in coarse sediments. These empirically defined points in the depth and sediment grain size gradients can be used to define reference habitats for the development of biocriteria. Benthic abundance and diversity were greatest in the mid-depth assemblage, conforming to predictions for benthic assemblages in regions of upwelling. Within the 500 km of coastline examined, latitude was not an important factor in defining assemblages. Received: 3 December 1999 / Accepted: 9 October 2000     

Indications from photosynthetic components that iron is a limiting nutrient in primary producers on coral reefs

Because iron is not available generally in oxygenated sea water, it may be a limiting factor in marine primary production. This hypothesis was tested in the context of Davies Reef, Latitude 18°50′S (one of the coral reefs in the central region of the Great Barrier Reef system). Samples were collected for study in the period August, 1980 to March, 1981. Sea water around the reef contained ≦2x10^-6 M Fe, surface sediments from the reef contained 66±26 (1 SD) ppm total Fe, and interstitial water near the surface contained ≧5x10^-7 M Fe. Thus, Fe constituted a trace component of the reef environment, but limited Fe should be available to algae associated with the sediments. Specific biochemical analyses to test the Fe status of benthic photosynthetic organisms were carried out with a common blue-green alga, Phormidium sp., and a ubiquitous symbiotic dinoflagellate, Gymnodinium microadriaticum (zooxanthellae). The blue-green alga contained the electron transport protein, flavodoxin, which is found only in Fe-deficient organisms. Supporting evidence for Fe stress in this organism included chlorosis in the presence of plentiful biliprotein, and very low extractable photosynthetic cytochrome, c-553. The latter observations were shown to be the result of Fe deficiency in laboratory cultures of a blue-green alga, Synechococcus sp. These cultures showed that production of flavodoxin is not a universal response of algae to Fe stress, but that lowered cellular concentrations of Fe-containing proteins involved in photosynthesis probably is universal. The zooxanthellae from a soft coral, Sinularia sp., had three-fold lower total Fe and ferredoxin (an electron transport protein), than the same alga from a clam, Tridacna maxima. Thus, some algae in symbiotic associations may also suffer Fe-deficiency. It was concluded that the degree and extent of Fe-stress in primary producers on a coral reef may influence growth rates, biomass, and distribution of species.     

Fish feeding on mobile benthic invertebrates: influence of spatial variability in habitat associations

Patterns of habitat association and foraging were examined for a group of tropical goatfishes (family Mullidae) that feed on mobile benthic invertebrates at Lizard Island (Great Barrier Reef). All goatfish possess barbels that disturb the substratum during feeding. Foraging methods were examined for the six most common species and used in conjunction with data on habitat associations to estimate the distribution and potential impact on the benthic invertebrate assemblage of foraging-related disturbance. Particular species exhibited broad habitat associations which differed little over two surveys (January 1989, January 1990). All species showed different preferences for the substrata they foraged. Preferences for substrata exhibited by the most common reef-associated species, Parupeneus multifasciatus, differed among locations separated by 1 km, between sites 150 m apart, and between depths (shallow and deep). Habitat preferences changed with ontogeny. Based on their habitat associations and foraging preferences, species were divided into habitat generalists and specialists. Specialists associated primarily with soft sediments. Habitat generalists, such as P. multifasciatus and P. cyclostomus, are likely to have an impact on their mobile invertebrate prey that is localised, diffuse and transitory, making any experimental analysis difficult and expensive. Habitat specialists form a guild of fishes with complementary feeding modes that efficiently exploit soft sediments and are more amenable to experimental manipulation. Experiments designed to detect the impact of foraging by these fishes must be repeated at different locations and times and must account for depth differences in foraging pressure.     

Light quality and concentration of proteins,RNA, DNA and photosynthetic pigments in two species of marine plankton algae

Chlorophyll, protein, DNA and RNA concentrations in cultures ofCyclotella nana (Hustedt) andDunaliella tertiolecta (Butcher) were higher in blue light and lower in green light than in white light of the same intensity. Total carotenoid concentrations were highest in green light. Total pigment concentrations were highest in cells grown in blue light, lowest in those from green light. The relative changes in pigment concentrations associated with differences in spectral composition of the radiation are comparable to those often observed in phytoplankton from various depths in stratified natural water. Light adaptation in algae as a response to light quality is suggested. The chemical composition of plankton algae can be expected to vary considerably with depth.     

The structure of subtidal algal and invertebrate assemblages at the Chatham Islands,New Zealand

We examined the distribution and abundance of organisms on subtidal rocky reefs at nine sites around the Chatham Islands, a remote group 780 km east of southern New Zealand. We sampled five depth strata ranging from 1 to<16 m to identify spatial patterns in the abundance of algae and invertebrates and to assess their variation within and among sites. This information is used to discuss hypotheses concerning community structure at this remote locality. Several patterns were apparent. The immediate subtidal was occupied by the southern bull kelp Durvillaea spp. A suite of 11 fucalean species were dominant to a depth of 10 m with an average abundance of 28 m^-2, while one species, Carpophyllum flexuosum, occurred mostly in deeper water. Only two laminarian species of algae were present at the islands. The indigenous Lessonia tholiformis was abundant at 2.5 to 15 m and was not found in deeper water, while the giant kelp Macrocystis pyrifera was abundant at two sites in 12 to 18 m. The commercially valuable abalone Haliotis iris was extremely abundant in shallow water, with an overall mean of 6 m^-2 at 5 m. The sea urchin Evechinus chloroticus was common, but reached high densities only in small (<25 m²) patches. The characteristic urchin-dominated zones reported in kelp beds world-wide were not seen. There was considerable site-to-site variation in the occurrence and abundance of individual species. Some differences between sites were associated with shelter from swell (e.g. M. pyrifera was found only in sheltered sites) and physical habitat (e.g. juvenile H. iris were found only beneath boulders inshore), but much of the variation could not be explained by physical or depth-related factors alone. We hypothesize that the differences in these kelp bed assemblages compared to mainland New Zealand are partially due to the high degree of endemism at the Chatham Islands. Local variation cannot be explained by herbivory, and is most likely the result of the various life-history characteristics of the major habitat-forming species, the large brown algae.     

Acoustic Observations of Bottom Surge From Dredged Material Discharge in the Open Ocean

Abstract

Bottom surges generated from dredged material discharges in the open ocean have been observed using high frequency acoustic concentration profilers in several field studies during the past five years. the locations, water depths, bottom slopes, oceanographic conditions, and dredged material composition differed from study to study. Observed surges at three dredged material disposal sites may develop more than one surge peak for a single discharge. for water depths of the order of 10 m, surge height of the leading peak was estimated to be about one quarter of the water depth. for water of greater depth, of the order of 100 m, surge height reached 70 m, about 70% of the water depth. Surge height is established instantaneously when dredged material hits the bottom, and remains relatively constant as the surge advances horizontally. Total surge length reached 150 m for water depths of 10 m when measured from the impact point to the leading edge. for water depths of more than 100 m, the surge length reached more than 100 m. Length of the leading surge peak was as large as 45 m at this water depth.

Dimensional analysis was applied to relate the surge height of the leading surge peak to discharge parameters and oceanographic conditions. Results showed that the ratio of surge height to water depth was proportional to 1/10 power of the ratio of discharge volume to the third power of water depth.     

Atypical plant–herbivore association of algal food and a kleptoplastic sea slug (Elysia clarki) revealed by DNA barcoding and field surveys

The identity of food sources and feeding preferences of specialist herbivores have been commonly inferred from spatial associations between consumer and food items. However, such basic information for well-known marine herbivores, sacoglossans (sea slugs), and their algal diets remains disappointingly lacking, especially from field studies. The sacoglossan, Elysia clarki (Pierce et al. in Molluscan Res 26:23–38, 2006), is kleptoplastic and sequesters chloroplasts from algal food to photosynthesize, so DNA identification of sequestered chloroplasts was employed to verify the algal species fed upon by the slug across its geographic range. The molecular information on the algae consumed by E. clarki was combined with field surveys of slugs and algae in slug habitats in the Florida Keys in July and August of 2008 in order to evaluate whether the diet of this herbivore could be predicted based on its spatial association with algae in the field. A considerable mismatch between food availability and kleptoplast identity was recorded. E. clarki commonly occupied areas devoid of potential food and often contained symbiotic plastids from algal species different from those most frequently found in the surveyed habitats. In three of the four study sites, algal species present were poor predictors of slug diet. These findings suggest that the photosynthetic capability of E. clarki may release the slug from the constraint of requiring proximity to its food sources and may allow for the potential lack of spatial coupling between this herbivore and its algal food. This combination of field surveys and DNA barcoding provided critical and previously unavailable information on herbivore feeding in this marine system.     

Nematode community composition in hydrothermal vent and adjacent non-vent fields around Myojin Knoll,a seamount on the Izu-Ogasawara Arc in the western North Pacific Ocean

In contrast to specific large benthic invertebrates in chemosynthetic ecosystems such as hydrothermal vents, meiofaunal communities in such habitats have been reported to have strong taxonomic overlap with meiofauna in the adjacent “normal” environments. However, meiofauna have only recently been included in studies of those environments and detailed information on these communities is still rare. This is especially true in the Northwest Pacific Ocean, even though there are many seamounts with active vents in the calderas of the region. Nematode community composition at the genus level in sediments from a hydrothermal vent field in the caldera of Myojin Knoll (32°06′N, 139°52′E, depth 1,300 m), a seamount on the Izu-Ogasawara Arc, Japan, was investigated for the first time and was compared with adjacent non-vent areas inside and outside the caldera. Multivariate analyses showed that the composition of nematodes in the hydrothermal field was significantly different from that in the non-hydrothermal fields around the caldera. However, the common genera, such as Oxystomina, Pareudesmoscolex, Desmoscolex, and Microlaimus were found in two, or all three vent fields while their rank contributions differed among the three fields. When the data from Myojin Knoll were compared with those from other deep-sea vent environments in different regions (e.g., North Fiji Basin, East Pacific Rise, Mid-Atlantic Ridge), the nematode composition in the vent field of the Myojin caldera was more similar to that of the non-vent fields around the caldera than the composition in vent fields of other regions. These data from the Northwest Pacific Ocean also suggest the absence of long-range transport systems and local adaptations for meiofauna in hydrothermal vent fields.     

Capability of dynamic photoinhibition in Arctic macroalgae is related to their depth distribution

The capability of several macroalgal species to protect photosynthesis from excessive irradiance by dynamic photoinhibition was investigated relative to their depth distribution in summer 1995 in the Kongsfjord (79°N; 12°E, Ny Ålesund, Spitsbergen, Norway). Photoinhibition of photosynthesis was induced by exposure of algae from different water depths to a high photon fluence rate of 500?μmol?m^?2?s^?1 for 2?h. Changes in optimal quantum yield (F _v/F _m) were measured during the inhibition phase. Recovery of photosynthesis was subsequently induced by dim white light (10?μmol?m^?2?s^?1) and observed as changes in the variable fluorescence. With a newly developed mathematical model different parameters of the response kinetics of inhibition and recovery were calculated and related to the depth distribution of each algal species. It is shown that two components with slow and fast reaction kinetics, respectively, are involved in photoinhibition and recovery of photosynthesis. Their possible molecular bases are discussed. The half-life time (τ) of the inhibition and recovery phases, i.e. the time necessary to reach half maximal response, is clearly related to the depth distribution of the investigated species. Algae collected close to the water surface show a fast reaction of both photoinhibition and recovery and, hence, have a low τ. With increasing depth the reactions become slower and τ increases. τ was highest in deep water algae. Further analysis of the reaction kinetics in Laminaria saccharina shows that the relative proportion of the two kinetics involved change with the collection depth. In contrast, a significant difference in the reaction rates of both kinetics was not observed.     

Temporal and spatial variation in protein,carbohydrate, and lipid levels in <Emphasis Type="Italic">Corallium rubrum</Emphasis> (Anthozoa,Octocorallia)

Red coral (Corallium rubrum) is an important component of the Mediterranean coralligenous habitat. The present study analyzes the relationship between energy storage molecule concentration (i.e. tissue balance of protein–carbohydrate–lipid levels) and the gonadal output in two populations located at different depths (16–18 m and 40–45 m depth) through a seasonal cycle (2002–2003). In June 2003, another six populations have been sampled to compare medium-scale geographical variation. The colonies sampled were less than 6 cm high, thus representing the majority of the population in the studied area. There was no clear relationship between energy storage (i.e. carbohydrate and lipid levels) and gonadal output, nor in the seasonal cycle or the spatial variation. A clear-cut seasonal trend of energy storage was detected only in the shallower population. The water temperature was warmer at 20 m depth and the water transparency (Secchi disk) was also higher (lower seston concentration) in 2003 when the same periods in 2002 and 2003 were compared (May–August). Carbohydrates seemed to be more sensitive to food constraints than lipids. The partial mortality detected in summer 2003 in the sampling area appeared to be recorded in the carbohydrate and lipid levels of this species, especially in the shallow population. The biochemical levels prove to be a useful tool to detect unusual environmental conditions that may cause partial or total mortality in benthic suspension feeders.     

GPS and time-depth loggers reveal underwater foraging plasticity in a flying diver,the Cape Cormorant

Knowledge on how divers exploit the water column vertically in relation to water depth is crucial to our understanding of their ecology and to their subsequent conservation. However, information is still lacking for the smaller-bodied species, due mostly to size constraints of data-loggers. Here, we report the diving behaviour of a flying diving seabird, the Cape Cormorant Phalacrocorax capensis, weighing 1.0–1.4 kg. Results were obtained by simultaneously deploying small, high resolution and high sampling frequency GPS and time-depth loggers on birds breeding on islands off Western South Africa (34°S, 18°E) in 2008. In all, dive category was assigned to all dives performed by 29 birds. Pelagic dives occurred almost as frequently as benthic dives. Pelagic dives were shallow (mean: 5 m) and took place over seafloors 5–100 m deep. Benthic dives were deeper, occurring on seafloors mainly 10–30 m deep. Dive shape was linked to dive category in only 60% of dives, while the descent rate, ascent rate and bottom duration/dive duration ratio of a dive best explained its dive category. This shows that only the concomitant use of tracking and depth tags can adequately classify diving strategies in a diver like the Cape Cormorant. Diet was mainly Cape Anchovy Engraulis encrasicolis, suggesting that birds probably displayed two contrasted strategies for capturing the same prey. Flexible foraging techniques represent an important key to survival inside the highly productive but heterogeneous Benguela upwelling ecosystem.     

In situ filtering and ingestion rates of deep-sea benthic boundary-layer zooplankton in the Santa Catalina Basin

In situ rates of filtration, particulate ingestion, and carbon ingestion of deep-sea benthic boundary-layer zooplankton were determined in December 1984 in the Santa Catalina Basin, at 1 300 m depth in the California Borderland, by a short-term radioisotope-incorporation technique. Zooplankton were collected at 1 or 50 m above the bottom with an opening-closing net system on a submersible, and incubated at depth with labelled amino acids in special cod-end chambers. Concentrations of particulate material and particulate organic carbon in the ambient water were also measured. The zooplankton had a median weight-specific filtration rate of 12.4 ml (mg dr. wt)^-1 h^-1 and a median carbon ingestion rate of 5.4 g C (mg dr. wt)^-1 h^-1. Filtration rates were not significantly different from those in similar experiments in the north Atlantic at 2 175 m depth or Narragansett Bay in the winter, although the medians of the deep-sea experiments were lower than for the Bay. In the Santa Catalina Basin, rates from experiments at 1 m above the bottom in more turbid water were not significantly different from those at 50 m above the bottom in clearer water. These deep-sea benthic boundary-layer zooplankton may have the potential to respond to food pulses, and their relatively high ingestion rates suggest that they could have significant effects on particulate, chemical, and bacterial processes in the near-bottom water column.