Port Foster Research Articles

Formation of Stanley Patch volcanic cone: New insights into the evolution of Deception Island caldera (Antarctica)

Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica, with more than 20 explosive eruptive events registered over the past centuries. Recent eruptions (1967, 1969, and 1970) and volcanic unrest episodes (1992, 1999, and 2014–2015) demonstrate that volcanic activity is likely occurring in the future. This is of special concern for scientists, logistic personnel, and tourists, since the South Shetland Islands are an important tourist destination and host numerous year-round and seasonal scientific stations and base camps. Significant efforts have been made to understand the complex magmatic and volcanic evolution of Deception Island with special interest on its subaerial part. However, studies on submerged volcanic cones within Port Foster, the sea-flooded part of Deception Island's caldera depression, are comparatively scarce. Here, we provide a full characterization of Stanley Patch volcano, the largest of these volcanic edifices. Estimated morphometric parameters based on new multibeam bathymetric data, supported by petrographic and chemical observations from rock samples collected on the crater rim, reveal that Stanley Patch volcano grew in a subaerial environment. This result, combined with previous findings and new sedimentological evidence from our ultra-high resolution seismic profiles, allow to further detail the island's geologic evolution since the caldera collapse. We conclude that the complete flooding of Port Foster could have only occurred after the formation of Stanley Patch volcano, i.e. during the last ~2000 years, and in a time period of a few days or less.

Volcanism and rapid sedimentation affect the benthic communities of Deception Island, Antarctica

Deception Island is amongst the most active volcanoes in the Southern Ocean, with over 20 explosive eruptions in the last ca. 200 years. The eruption that formed the caldera at Deception Island occurred 3980 ± 125 calendar years Before Present, and it is the largest eruptive event documented in Antarctica during Holocene. Since then, post-caldera volcanic activity has comprised many scattered eruptive vents across the island. Mortality of benthic organisms has been reported during the most recent eruptions occurred on the island, in 1967, 1969, and 1970 Common Era (CE), with very low abundances of organisms during the 1967–1973 CE period. Within the sea-flooded part of the caldera depression, named Port Foster, a submarine volcanic axis with several volcanic cones is observed. An interdisciplinary team sampled the best morphologically preserved volcanic edifice within Port Foster, the so-called Stanley Patch. Geophysical data traced the volcano and characterized its morphology and inner structure. Underwater scuba sampling allowed to acquire sediment and rock samples, photographs and video images of the benthic organisms and seascape. Morphology of Stanley Patch cone and textural characteristics of the collected pyroclastic rocks indicate that the volcanic edifice was originated during an explosive eruption. Furthermore, the lack of palagonitization, quenched pyroclast margins, and hyaloclastite deposits indicate that this cone has formed on-land, before the caldera floor became inundated by the seawater, highlighting the complex intra-caldera evolution of Deception Island. A sediment core from the crater was collected for sedimentological, and geochemical analysis. Antarctic climate and seasonal sea ice, together with organic degradation due to high sedimentation rates, explain the low total organic carbon data measured. The volcanic history of the island has probably avoided the development of a stable benthic community over time, similar to other Antarctic shallow communities. Moreover, the current geomorphological conditions still shape different benthic communities than in the surrounding coastal ecosystems. Stanley Patch, and the whole Port Foster, provide a natural laboratory for benchmarking the reestablishment of benthic communities on a volcanic-influenced shallow marine environment, offering relevant data for future studies evaluating global climate change effects on the Antarctic seabed.

First screening of biocides, persistent organic pollutants, pharmaceutical and personal care products in Antarctic phytoplankton from Deception Island by FT-ICR-MS

In recent years, the Antarctic territory has seen a rise in the number of tourists and scientists. This has led to an increase in the anthropogenic footprint in Antarctic ecosystems, namely in terms of emerging contaminants, such as Biocides, Persistent Organic Pollutants (POPs) as well as Pharmaceutical and Personal Care Products (PPCPs). Yet scarce information on the presence of these emerging contaminants is available for trophic compartments, especially the phytoplankton community. Using high resolution Fourier-transform ion cyclotron-resonance mass spectrometry (FT-ICR-MS), an untargeted screening of the metabolome of the phytoplankton community was performed. Seventy different contaminant compounds were found to be present in phytoplankton collected at two sites in Port Foster Bay at Deception Island. These emerging contaminants included 1 polycyclic aromatic hydrocarbon (PAH), 10 biocides (acaricides, fungicides, herbicides, insecticides and nematicides), 11 POPs (flame retardants, paints and dyes, polychlorinated biphenyl (PCB), phthalates and plastic components), 5 PCPs (cosmetic, detergents and dietary compounds), 40 pharmaceutical compounds and 3 illicit drugs. Pharmaceutical compounds were, by far, the largest group of emerging contaminants found in phytoplankton cells (anticonvulsants, antihypertensives and beta-blockers, antibiotics, analgesic and anti-inflammatory drugs). The detection of several of these potentially toxic compounds at the basis of the marine food web has potentially severe impacts for the whole ecosystem trophic structure. Additionally, the present findings also point out that the guidelines proposed by the Antarctic Treaty and Protocol on Environmental Protection to the Antarctic Treaty should be revisited to avoid the proliferation of these and other PPCPs in such sensitive environments.

Warming and Wrack Supply Will Accelerate CO2 Emission and Nutrients Release on Antarctic Sedimentary Shores: A Case Study on a Volcanic Island

The shifts in soil metabolism as a response to warming and wrack subsidies on Antarctic sedimentary shores have not been studied to date. With this aim, macroalgal deposits, as well as inorganic nutrients and CO2 emission were quantified along the shores of Port Foster, on Deception Island, Antarctic Peninsula. The results indicated a positive relationship between the amount of wrack supplies and sediment metabolism, measured both as CO2 emission through the sediment surface and as amount of inorganic nutrients released to the interstitial pore water. The effect of warming on algal wrack decay was analyzed in a manipulative field experiment where passive open-top chambers (OTCs) were used to increase soil temperature. By doing this, temperature raised by 0.9°C under patches of the red macroalgae Palmaria decipiens, whereas there was an increase of 2.4°C on bare sand. The results indicated that a small warming accelerated mineralization rates of C, N and P of the algal biomass, without significant changes in the bulk of inorganic nutrients released. Over 12 days of experiment, 8.3% of the total C in algal tissues was released as CO2 in the OTC plots, compared to 6.4% at ambient temperature. CO2 emission in bare sand plots warmed with OTCs was three times the amount measured in the ambient plots. Collembola was the dominant soil fauna, with densities negatively affected by warming and positively related to the organic content of sediment. This study confirms the key role of sandy shores in recycling ocean derived organic matter, highlighting the sensitivity of Antarctic ecosystems to a changing scenario of climate change that predicts significant increases in temperature over the next few decades.

Volcano-tectonic dynamics of Deception Island (Antarctica): 27 years of GPS observations (1991–2018)

Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica. In the 1988–1989 austral summer, after the most recent eruptive process on the island (1967–1970), monitoring of volcanic activity through geophysical and geodetic techniques was resumed by Spanish and Argentinean scientists. In order to monitor the island's tectonic and volcanic behavior, a geodetic network was deployed. Currently, this network consists of 15 geodetic benchmarks located around Port Foster, Deception's inner bay open to the sea. Two additional geodetic benchmarks were installed outside Deception Island to be used as reference benchmarks for the differential positioning strategy. Since 1991–1992, geodetic ground-displacement velocities between the successive austral summer Antarctic campaigns have been computed and analyzed.The overall geodynamic behavior of Deception Island within the South Shetland Islands, Antarctic Peninsula and Bransfield Basin regional environment has been analyzed from geodetic ground-displacements. Results obtained demonstrate that Deception and Livingston island have a similar behavior derived from the Bransfield Basin extension and the Phoenix micro-plate subsidence processes. However, Deception Island is also highly influenced by its volcanic activity.Deception Island's volcanic behavior between 1991 and 2018 is shown by the velocity field, strain tensors and pressure source evolution obtained from the ground-displacements at the geodetic benchmarks. During this time period, it is possible to identify different inflation and deflation phases separated by transitional (or mixed) stages of extension without uplift and compression without subsidence. The most representative inflation and deflation periods were analyzed in detail, to show how they correlate with high and low seismic activity, respectively. The transitional or mixed stages, seem to be the precursors of the next inflation or deflation phase being the Bransfield basin rifting and NW-SE extension the potential related process.Finally, we have analyzed the processes that occurred prior to the volcanic unrests of 1999–2000 and 2012–2013. In both cases, an increase in detected seismic activity and/or soil and seawater temperature was observed and a mixed phase of extension without uplift seems to be precursory to the volcanic unrest. The correlation between the inflation processes, identified by ground-displacement of the network geodetic benchmarks, the increase in seismicity and the increment of soil and seawater temperature makes these transitional mixed phases potential precursors of Deception Island's volcanic unrest periods.

Hydrodynamic modelling of Port Foster, Deception Island, Antarctica

AbstractOver the last decade, the Antarctic continent has been the object of intensive scientific programmes. However, the emphasis of these studies rarely focuses on the Antarctic as a source of potential elements such as mercury. The release of mercury to the environment is known to occur at Deception Island, associated with volcanic activity. In this study, a 3D hydrodynamic model was used to assess the role of water circulation on the dispersion of released mercury. Sea level variation and tidal circulation data were obtained. Residence time was calculated using two different approaches. Internal tide generation in summer and winter were recognized and the barotropic tidal components obtained. Lagrangian tracers were used to depict particle circulation (simulating particulate mercury) in a three month summer simulation for barotropic and baroclinic conditions. The results show that particles accumulate in the northern and western parts of the bay. It is acknowledged that the results of the 3D model are associated with a non-negligible uncertainty, which can only be reduced with an ongoing commitment to monitoring. The findings of this study indicate that mercury accumulation is occurring in Port Foster (Deception Island), which is a potential threat to the local ecosystem.

Macroinvertebrate communities from the shallow soft-bottoms of Deception Island (Southern Ocean): A paradise for opportunists

Deception Island (South Shetland Islands) is an atypical spot in its Antarctic context, being a still active volcano with a submerged caldera. Although the sea-floor of its enclosed bay, Port Foster, has been extensively studied from 40 m down, little is known about the macrozoobenthic composition of its shallower areas. The aim of this study was to characterize the so far unexplored soft-bottom marine macroinvertebrate communities living within the first few meters depth in Port Foster. Eight sampling stations were selected, and three replicates per station and depth (5 and 15 m) were collected by SCUBA diving using 0.008 m-2 corers. Six clusters of samples were distinguished, showing a high variability in the composition of the shallow-water macrofauna. This heterogeneity did not appear to be related to the proximity of the sites to the open sea (entrance of the caldera) or depth, nor to the sediment type or the organic matter content. Overall, the assemblages within each cluster were generally dominated by highly abundant opportunistic species, including the annelids Capitella perarmata, Mesospio moorei, Leitoscoloplos kerguelensis, Apistobranchus glacierae, and Tharyx cincinnata, the amphipod Cheirimedon femoratus, and the bivalve Aequiyoldia eightsii. The remarkably high densities reported in several stations, suggest that the shallow-water environment of Port Foster is highly productive. In light of these results, we propose a general trophic web for the shallow waters of Port Foster linking the unusually high densities of macroinvertebrates with the also high occurrence of megafaunal echinoderms present in this area.

Hydrography and dynamics of Port Foster, Deception Island, Antarctica

AbstractThe circulation and water masses of Port Foster, Deception Island, were studied using conductivity-temperature-depth stations inside and outside the semi-enclosed bay and an array of bottom temperature sensors moored around the perimeter of the bay over two weeks in the summer of 2012. Inside Port Foster, the water column is divided into two layers separated by a temperature-forced, seasonal pycnocline at ~40–60 m. The circulation of the upper layer is in an anticlockwise direction, with mean geostrophic currents of ~0.04–0.10 ms-1. The lower layer, from ~60 m to the seabed, shows coastal-trapped waves travelling in a clockwise direction, possibly triggered by local wind gusts. Local sea ice melt in areas surrounding the underwater hot springs of Pendulum Cove appears as a fresh, warm anomaly down to 30 m.

Unusual signals recorded by ocean bottom seismometers in the flooded caldera of Deception Island volcano: volcanic gases or biological activity?

AbstractAn ocean bottom seismometer (OBS) network was deployed for 1 month at Deception Island volcano, Antarctica, in early 2005. Although only two volcano-tectonic and three long-period events were observed, the three OBSs located > 2 km apart inside the caldera detected over 3900 events that could not be attributed to known volcanic or hydrothermal sources. These events are found on one instrument at a time and occur in three types. Type 1 events resemble impulsive signals from biological organisms while type 2 and type 3 events resemble long-period seismicity. The largest number of events was observed in a region of volcanic resurgence and hydrothermal venting. All three types occur together suggesting a common cause and they show evidence for a diurnal distribution. The events are most likely to be due to aquatic animals striking the sensors, but a geological source is also possible. In the first case, these signals indicate the presence of a biological community confined to the caldera. In the second case, they imply widespread hydrothermal activity in Port Foster. Future OBS experiments should bury the seismometers, include a hydrophone, deploy instruments side-by-side, or include a video camera to distinguish between biological and geological events.

Enhancement of sub-daily positioning solutions for surface deformation monitoring at Deception volcano (South Shetland Islands, Antarctica)

Deception Island is one of the most visited places in Antarctica. There are biological, geological, and archeological features that are major attractions within Port Foster, its horse shoe-shaped natural inner bay, and two scientific bases that are occupied during austral summers. Deception Island is an active volcano, however, and needs to be monitored in order to reduce risk to people on the island. Surface deformation in response to fluid pressure is one of the main volcanic activities to observe. Automated data acquisition and processing using the global navigation satellite systems allow measurements of surface deformation in near real time. Nevertheless, the positioning repeatability in sub-daily solutions is affected by geophysical influences such as ocean tidal loading, among others. Such periodic influences must be accurately modeled to achieve similar repeatability as daily solutions that average them. However, a single solution each 24 h will average out the deformation suffered during that period, and the position update waiting time can be a limitation for near real-time purposes. Throughout the last five austral summer campaigns in Deception, using simultaneous wireless communications between benchmarks, a processing strategy was developed to achieve millimeter-level half-hourly positioning solutions that have similar repeatability as those given by 24-h solutions. For these half-hourly solutions, a tidal analysis was performed to assess any mismodeling of ocean tide loading, and a discrete Kalman filter was designed and implemented to enhance the sub-daily positioning repeatability. With these solutions, the volcano-dynamic activity resulting in localized surface deformation for the last five austral summer campaigns is addressed. Although based on only three carefully located benchmarks, it is shown that Deception has been shortening and subsiding during these last 4 years. The method’s accuracy in baselines up to a few hundred kilometers assures its applicability to other volcanoes worldwide.

The diversity, extracellular enzymatic activities and photoprotective compounds of yeasts isolated in Antarctica.

The diversity of yeasts collected from different sites in Antarctica (Admiralty Bay, King George Island and Port Foster Bay and Deception Island) and their ability to produce extracellular enzymes and mycosporines were studied. Samples were collected during the austral summer season, between November 2006 and January 2007, from the rhizosphere of Deschampsia antarctica, ornithogenic (penguin guano) soil, soil, marine and lake sediments, marine water and freshwater from lakes. A total of 89 isolates belonging to the following genera were recovered: Bensingtonia, Candida, Cryptococcus, Debaryomyces, Dioszegia, Exophiala, Filobasidium, Issatchenkia (Pichia), Kodamaea, Leucosporidium, Leucosporidiella, Metschnikowia, Nadsonia, Pichia, Rhodotorula, and Sporidiobolus, and the yeast-like fungi Aureobasidium, Leuconeurospora and Microglossum. Cryptococcus victoriae was the most frequently identified species. Several species isolated in our study have been previously reported to be Antarctic psychophilic yeasts, including Cr. antarcticus, Cr. victoriae, Dioszegia hungarica and Leucosporidium scottii. The cosmopolitan yeast species A. pullulans, C. zeylanoides, D. hansenii, I. orientalis, K. ohmeri, P. guilliermondii, Rh. mucilaginosa, and S. salmonicolor were also isolated. Five possible new species were identified. Sixty percent of the yeasts had at least one detectable extracellular enzymatic activity. Cryptococcus antarcticus, D. aurantiaca, D. crocea, D. hungarica, Dioszegia sp., E. xenobiotica, Rh. glaciales, Rh. laryngis, Microglossum sp. 1 and Microglossum sp. 2 produced mycosporines. Of the yeast isolates, 41.7% produced pigments and/or mycosporines and could be considered adapted to survive in Antarctica. Most of the yeasts had extracellular enzymatic activities at 4°C and 20°C, indicating that they could be metabolically active in the sampled substrates.

Evidence for hydrothermal venting and sediment volcanism discharged after recent short-lived volcanic eruptions at Deception Island, Bransfield Strait, Antarctica

The results of a combined geophysical and geochemical research programme on Deception Island, an active volcano at 62°43′S, 60°57′W in Bransfield Strait (Antarctica), are presented. Ultrahigh-resolution acoustic data obtained with a TOPAS (TOpographic PArameter Sonar) system and multibeam bathymetry (Simrad EM1000) allow a detailed analysis of submarine vents in Port Foster, the submerged caldera of Deception Island. The data show three different types of seafloor structures: low-relief mounds, high-relief mounds (‘wasp nest’-like) and spire-like structures. We interpret these structures as products of sediment volcanism and seeps caused by heating and boiling of pore fluids in gas-charged sediments, and related to recent short-lived volcanic events, possibly those that occurred in 1967, 1969 and 1970. In addition, subsurface vertical disturbed zones, formed by increased amplitude and phase-inverse reflectors beneath the mounds, suggest the presence of fluidised and brecciated sediments within hydrofracture systems. A key finding of this study is that there appears to be a close relationship between the submarine mounds detected by our ultrahigh-resolution seismic study, geochemical haloes, fault-pathways and present-day thermal anomalies in surface waters. We suggest that seafloor hydrofracture systems and subsurface pipes can be re-used as fluid migration pathways, resulting in hydrothermal seeps and vents on the seafloor, possibly up to decades after coeval volcanic eruptions.

Seasonal changes of dissolved nutrients within and around Port Foster Deception Island, Antarctica

Abstract Temporal and spatial distribution of dissolved macronutrients (ammonia, nitrate, phosphate and silica) and productivity were investigated within and around Port Foster, the flooded 160-m-deep caldera of Deception Island, Antarctica. This study was part of the Erupt Project, which included five seasonal cruises over a complete annual cycle during 1999–2000. Seawater samples were collected and physical properties were monitored from seven stations within Port Foster and 12 stations in the adjacent Bransfield Strait. In addition, shallow-water and beach interstitial-water samples were collected along the shorelines of the peripheral coves. Port Foster macronutrient/depth profiles were typical for a normal shallow seawater column in a polar region. The water column in early austral spring was well mixed and changed to a stratified water column with a weak thermocline during the summer. By early winter, the thickness of the well-mixed surface layer increased until the entire water column returned to well-mixed conditions. This early winter transition from stratified conditions to well-mixed conditions occurred in June and appeared to be abrupt. During the seasons of light limitation and low-primary productivity, local currents were effective at redistributing dissolved biochemical components throughout the bay. During the summer season, the dissolved nutrient and oxygen distributions reflected consumption of nutrients by primary producers. The mid-depth maximum observed in the ammonia profiles implies the excretion of metabolites from resident animal populations. Residence time of dissolved ammonia must have been shorter than the circulation time within Port Foster because ammonia is not as uniformly distributed during the summer months as it was during the winter and spring. Dissolved nitrate concentrations in the Bransfield Strait during this study were similar to those measured in previous studies. The mean concentrations of phosphate, nitrate, and silica in the beach interstitial samples were significantly higher (2.8–9.5 times) than in the shore, offshore and CTD samples. Possible sources for the high phosphate, nitrate, and ammonia concentrations in the beach interstitial and shore waters include decaying organic matter and bird and mammal excrement. Elevated silica concentrations appear to be associated with hydrothermal heating of beach and near-shore waters. However, the elevated macronutrient concentrations measured in the beach interstitial water were not traceable beyond 5 m of the shoreline. Phytoplankton biomass in Port Foster exhibited temporal variability similar to other coastal and continental shelf zones (CCZ) of the Antarctic Peninsula. Blooms in February and November 2000 were dominated by the centric diatoms Thalassiosira spp. and Rhizosolenia spp. Chlorophyll a (chl a ) values of 15 and 19 mg m −3 in Port Foster during these blooms were comparable to maximum-recorded levels in western Antarctic Peninsula CCZ (30–40 mg chl a m −3 ), while chl a values from November 1999 and June 2000 (non-bloom conditions) corresponded to historical monthly chl a averages of western Antarctic Peninsula CCZ ( −3 ). During blooms, phytoplankton standing stock could account for about 15 μM nitrate, which corresponds to the observed surface nitrate depletion.

Fish populations of Port Foster, Deception Island, Antarctica and vicinity

The fish populations of Port Foster, Deception Island, South Shetland Islands, Antarctica, were investigated as part of the Erupt Antarctic ecosystem study. Surveys were conducted on five cruises between March 1999 and November 2000. Samples also were collected off Livingston Island and King George Island of the South Shetland Islands. Specimens were collected or observed using a multiple opening and closing net and environmental sampling system, otter trawls, benthic line-transect photography, and remotely operated vehicle video. Species composition, length, weight, reproductive condition, diet, habitat, and parasitic infestation were examined for the dominant fish species. Eleven species were collected, all in the suborder Notothenioidei. The fishes found in the survey are known to occur in the region and had diets similar to those found in other studies. Abundances of demersal fishes in Port Foster ranged from 0.05 to 0.10 individuals m−2 over the study period. Inshore shallow-water ( 30 m) habitats are identified in Port Foster and described. Port Foster may be a refuge for juvenile fishes such as Champsocephalus gunnari. Limited exchange with the surrounding waters also may limit the influence of recruitment and prey abundance fluctuations outside Port Foster. Trematomus scotti had heavy body cavity parasite infestation from Port Foster, possibly due in part to decreased benthic scour from large icebergs, allowing benthic parasites to persist.

Temporal dynamics of particulate matter fluxes and sediment community response in Port Foster, Deception Island, Antarctica

Abstract Time-series particle flux and seasonal sediment community oxygen consumption (SCOC) were measured in Port Foster (160 m water depth), Deception Island, Antarctica, beginning in March 1999 and continuing through November 2000. Sediment traps were moored at 50 and 20 m above bottom and collected sedimenting material for contiguous periods of 10 to 18.3 days. Fluxes of material increased in mid-winter of 1999 and 2000 but were more notable in 1999. Fluxes were higher in the deeper sediment trap and there was an inverse relationship between mass flux and % organic carbon and particulate total nitrogen. A piston-operated grab respirometer was deployed at 160 m depth for 35–60 h in November 1999, and in February, May/June, and November 2000, to measure SCOC and recover the sediment for organic carbon, nitrogen and pigment composition. SCOC, as an estimate of sediment community carbon demand, exceeded the organic carbon flux to the seafloor (supply), and alternative sources of organic carbon input to the benthos are discussed. Highest SCOC occurred in the austral summer during a particle-flux sampling hiatus in the summer of 2000. Fluxes were positively correlated with local wind speed measured at a terrestrial station positioned on a hill overlooking Port Foster. There was also a positive correlation between the particulate matter fluxes and the ratio of chlorophyll a to phaeopigments, an indicator of the “freshness” of material entering the sediment trap at 20 mab.

Weather, ice, and snow conditions at Deception Island, Antarctica: long time-series photographic monitoring

Abstract An autonomous weather station (Terrestrial station) was developed and deployed at Deception Island, Antarctica, an active volcanic island, to monitor the daily weather conditions as part of a long time-series marine ecosystem study of the sunken caldera, Port Foster. The principal components of the Terrestrial station were a time-lapse digital camera, ultrasonic wind sensor, controller, wind turbine generators, and batteries. The Terrestrial station was installed on a ridge at 200 m altitude overlooking Port Foster and the surrounding terrain from 9 March 1999 until 20 November 2000. Ice cover on Port Foster began in late July 2000 and was intermittently visible through early November. Daily averaged wind speeds ranged from 0.2 m s−1 in October to 47.4 m s−1 in June, with the prevailing direction from the southwest and less frequently from the northeast. Daily averaged air temperatures fluctuated from a low of −12.6°C in August 2000 to 2.7°C in March 1999. Weather conditions measured at Deception Island were generally consistent with those concurrently measured in the region of the South Shetland Islands. Ice cover in Port Foster was less pronounced in 1999 and 2000 than reported in previous years, suggesting regional warming.

The epibenthic megafaunal and benthic infaunal invertebrates of Port Foster, Deception Island (South Shetland Islands, Antarctica)

Abstract Otter trawl and grab samples (0.3 mm sieve) collected in Port Foster, Deception Island, from March 1999 to November 2000 as part of the ERUPT Antarctic ecosystem study were used to assess the status of the epibenthic megafaunal and benthic infaunal communities, which were heavily impacted by the volcanic eruptions of 1967–1970. Additional otter trawls were collected in coastal waters off Livingston and King George Islands to compare the epibenthic megafauna community of Port Foster with that of open coastal Antarctic environments. The epibenthic and infaunal communities of mid-bay Port Foster have significantly recovered since 1967 when mid-bay dredge and grab samples yielded a total of four individuals in two dredge hauls and an infaunal abundance of 40 individuals m −2 . Port Foster trawls from this study yielded an average of 26.2 taxa for the five sampling dates, with a cumulative total of 68 taxa. The epibenthic community at Port Foster was primarily composed of deposit feeding taxa with the ophiuroid, Ophionotus victoriae the dominant organism. Livingston and King George trawls yielded a total of 99 and 135 taxa, respectively, with a dominant suspension-feeding community of sponges and tunicates supporting a more diverse rich epibenthic fauna. Benthic infaunal abundance and biomass averaged 85,566.3 individuals m −2 and 121.951 g m −2 . Foraminifera, nematodes, and polychaetes were the most abundant infauna in Port Foster sediments representing 59.05%, 17.48% and 16.38% of total abundance, respectively. Bivalve mollusks and polychaetes were the major contributors to the biomass, with 48.375% and 45.294% of total wet weight, respectively. Abundant populations of microbiota (foraminiferans) and meiofauna (nematodes) suggest that, as in other benthic habitats, these small but numerous organisms play a key role in carbon utilization and the food web. Sediment type and food resources are major factors controlling the benthic community structures of Port Foster and Livingston and King George Islands. The accumulation of sediments in Port Foster from wind and melt-runoff associated with past volcanic activity limits the suspension feeding community and is a possible source of metals contamination. Warming of the Antarctic polar environment will likely increase sedimentation at Port Foster and open coastal areas as glaciers melt and land surfaces are exposed to wind and rain.

Distribution and abundance of marine bird and pinniped populations within Port Foster, Deception Island, Antarctica

Seabirds and pinnipeds were surveyed during four cruises from March 1999 to November 2000 at Port Foster, Deception Island, Antarctica. Abundances and distributions of three species of pinnipeds, Arctocephalus gazella (Antarctic fur seals), Leptonychotes weddelli (Weddell seals), and Lobodon carcinophagus (crabeater seals), and 11 species of marine birds were documented within Port Foster. A. gazella was the dominant pinniped within Port Foster; its abundance has increased since the 1986/87 austral summer season. A. gazella were concentrated at the entrance to Port Foster. More pinnipeds were observed during the austral summer than during the spring. The most dominant seabird, Pygoscelis antarctica (chinstrap penguin), was concentrated along the rocky cliffs behind the beaches where A. gazella hauled out. Larus dominicanus (kelp gull) and Daption capense (cape petrel) were the most dominant flying seabirds. All other seabird species were more widely distributed around Port Foster than P. antarctica. There was no clear trend in abundances of seabirds over the study period. It is possible that the protected area of Port Foster provides refuge for vagrants of colonies along the outer periphery of the island and as a stopover point for migrating species.

Seasonal variations in abundance, diel vertical migration, and population structure of Metridia gerlachei at Port Foster, Deception Island, Antarctica

Abstract During five cruises in a 1.5-yr period between February 1999 and November 2000, we studied the abundance, vertical distribution, and population structure of the calanoid copepod Metridia gerlachei (Giesbrecht) at Port Foster, a 160 m deep embayment of Deception Island, Antarctica. M. gerlachei was found at Port Foster year round with abundance peaking in early winter 2000, averaging about 200 copepods m−3 over the entire water column, and up to 800 copepods m−3 at mid-water depths. Diel vertical migration of the M. gerlachei population was observed during some parts of the year, while there was no evidence for seasonal vertical migration. Based on analysis of developmental stage-frequency analysis and abundance data, we speculate that M. gerlachei had three generations per year, began to spawn early in the spring, and had the strongest reproductive effort late in the fall. Using daily carbon ration estimates, M. gerlachei accounted for

Spatial and temporal variation in the abundance, distribution and population structure of epibenthic megafauna in Port Foster, Deception Island

Abundance and spatial distribution of epibenthic megafauna were examined at Port Foster, Deception Island, five times between March 1999 and November 2000. Camera sled surveys and bottom trawls were used to identify and collect specimens, and camera sled photographs also were used to determine abundances and spatial distributions for each species. The ophiuroid Ophionotus victoriae, the regular echinoid Sterechinus neumayeri, and one or more species of Porifera were the most abundant taxa during this sampling period. Abundances of O. victoriae varied throughout the annual cycle, peaking in June 2000, and were correlated positively with sedimentation rates. In contrast, abundances of S. neumayeri were consistent throughout the sampling period, except for a peak in June 2000, during austral winter. Peak abundances for both species coincided with a large number of small individuals, indicating apparent recruitment events for O. victoriae and S. neumayeri during this time period. Poriferans, as a group, had statistically similar abundances during each sampling period. Low-abundance species tended to be aggregated on both small and large spatial scales, their distributions probably influenced by reproductive method, gregarious settlement, and food availability. The spatial distribution of S. neumayeri in June 2000 and O. victoriae was random across multiple spatial scales, perhaps in response to food availability and broad environmental tolerances, respectively.