[Show abstract][Hide abstract] ABSTRACT: There is concern that the use of natural volcanic CO2 vents as analogs for studies of the impacts of ocean acidification on marine organisms are biased due to physiochemical influences other than seawater pH alone. One issue that has been raised is whether potentially harmful trace elements in sediments that are rendered more soluble and labile in low pH environments are made more bioavailable, and sequestered in the local flora and fauna at harmful levels. In order to evaluate this hypothesis, we analyzed the concentrations of trace elements in shells (an established proxy for tissues) of four species of gastropods (two limpets, a topshell and a whelk) collected from three sites in Levante Bay, Vulcano Island. Each sampling site increased in distance from the primary CO2 vent and thus represented low, moderate, and ambient seawater pH conditions. Concentrations of As, Cd, Co, Cr, Hg, Mo, Ni, Pb, and V measured in shells using ICP-OES were below detection thresholds for all four gastropod species at all three sites. However, there were measurable concentrations of Sr, Mn, and U in the shells of the limpets Patella caerulea, P. rustica, and the snail Osilinus turbinatus, and similarly, Sr, Mn, U, and also Zn in the shells of the whelk Hexaplex trunculus. Levels of these elements were within the ranges measured in gastropod shells in non-polluted environments, and with the exception of U in the shells of P. caerulea, where the concentration was significantly lower at the collecting site closest to the vent (low pH site), there were no site-specific spatial differences in concentrations for any of the trace elements in shells. Thus trace element enhancement in sediments in low-pH environments was not reflected in greater bioaccumulations of potentially harmful elements in the shells of common gastropods.
[Show abstract][Hide abstract] ABSTRACT: Marine macroalgae can release reactive oxygen species (ROS) upon wounding and grazing. Here we address the potential role of ROS in herbivore defense. We performed feeding assays in the presence of varying concentrations of hydrogen peroxide (H2O2), a common type of ROS. H2O2 inhibited feeding by a marine amphipod grazer, Gondogeneia antarctica, over broad levels of concentration, and its potency was strongly dependent on its rate of decay in natural seawater. Because it is possible that the inhibitory levels of H2O2 are encountered in the vicinity of a sympatric macroalgal wound, we suggest that H2O2 has the potential to act as a direct anti-grazing defense in marine ecosystems. Since some sympatric macroalgae release a burst of non-H2O2 ROS, we also performed experiments to evaluate the role of these naturally-produced ROS on sympatric grazers. The presence of wounded Ascoseira mirabilis (which releases a burst of non-H2O2 ROS after wounding) during a feeding assay inhibited feeding of G. antarctica compared to the presence of intact A. mirabilis. These data are consistent with a role for ROS as a direct anti-herbivore defense in nature. However, the data are also consistent with hypotheses that involve other putative activated anti-grazing defenses.
Journal of Experimental Marine Biology and Ecology 01/2014; 458:34–38. · 2.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Warming seawater temperatures and ocean acidification on the coastal western Antarctic Peninsula pose unique challenges to stenothermal marine invertebrates. The present study examines prospective sub-lethal effects of elevated temperature, pCO2, and resultant decrease in seawater pH, on righting behavior and maximal escape speeds for two common gastropods, the limpet Nacella concinna (Strebel) and mesogastropod snail Margarella antarctica (Lamy). Replicate individuals held in individual containers were exposed to four combinations of seawater temperature (1.5 °C — current average, 3.5 °C — projected average by 2100) and pH (pH 8.0 — current average, pH 7.8 — projected average by 2100 as a result of elevated pCO2 levels) for a period of 6 weeks. Following this chronic exposure, righting behavior, determined for the limpets as proportion to right over 24 h and for snails as time to right, as well as maximum escape speed following contact with a sea star predator were measured. We found no significant differences in proportions of limpets displaying the capacity to right among the four temperature–pH treatments. However, there was a significant temperature–pH interaction effect for mean righting times in snails, indicating that the effect of pH on the time to right is dependent on temperature. We found no significant effects of temperature or pH on mean maximal escape speed in limpets. Additionally, we observed a significant temperature–pH interaction effect for mean maximal escape speed in snails. These interactive effects make it difficult to make clear predictions about how these environmental factors may impact behavioral responses.
Journal of Experimental Marine Biology and Ecology 01/2014; 457:90–96. · 2.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Whale falls provide a substantial, nutrient-rich resource for species in areas of the ocean that may otherwise be largely devoid of food. We report the discovery of a natural whale fall at 1430 m depth in the cold waters of the continental slope off the western Antarctic Peninsula. This is the highest latitude whale fall reported to date. The section of the carcass we observed—the tail fluke—was more complete than any previously reported natural whale fall from the deep sea and in the early stages of decomposition. We estimate the entire cetacean to measure 5 to 8 m in length. The flesh remained almost intact on the carcass but the skin was missing from the entire section except for the end of the fluke, clearly exposing blubber and soft tissue. The absence of skin indicates rapid and homogenous loss. The dominant macrofauna present were crustaceans, including most prominently the lithodid crab Paralomis birsteini, and zoarcid fish typical of the ‘mobile-scavenger' successional stage. The density of mobile macrofauna was greatest on the carcass and declined to background levels within 100 m, indicating that they were attracted to the whale fall. This whale fall offers an important opportunity to examine the decomposition of a carcass under deep-sea conditions at polar latitudes.
Deep Sea Research Part A Oceanographic Research Papers 01/2014;
[Show abstract][Hide abstract] ABSTRACT: Land-based aquaculture facilities experience occasional hypercapnic conditions due to the accumulation of the metabolic waste product carbon dioxide. Pre-gonadal Lytechinus variegatus (horizontal diameter = 20 mm) were exposed to control (608 μatm pCO2, pH 8.1) or hypercapnic conditions (1738 μatm pCO2, pH 7.7) in synthetic seawater for 14 weeks. Sea urchins exposed to hypercapnic conditions exhibited significantly slower growth (reduced dry matter production), primarily due to reduced test production. Higher fecal production rates and lower ash absorption efficiency (%) in individuals exposed to hypercapnic conditions suggest the ability to process or retain dietary carbonates may have been affected. Significant increases in neutral lipid storage in the gut and increased soluble protein storage in the gonads of individuals exposed to hypercapnic conditions suggest alterations in nutrient metabolism and storage. Furthermore, organic production and energy allocation increased in the lantern of those individuals exposed to hypercapnic conditions. These results suggest chronic exposure to hypercapnic conditions alters nutrient allocation to organ systems and functions, leading to changes in somatic and reproductive production.
[Show abstract][Hide abstract] ABSTRACT: Hard bottom communities along the western Antarctic Peninsula region are dominated by thick macroalgal forests, which support high densities of mesograzers, particularly amphipods, and also numerous gastropods. The macroalgae are chemically defended from consumption by the mesograzers and other herbivores and they provide the mesograzers a chemically defended refuge from predation by omnivorous fish. The macroalgae benefit in return because the mesograzers remove epiphytic algae from them. Since these two assemblages are major components of the community, this can be viewed as a community-wide mutualism. Most subcomponents of these interactions have also been documented in lower latitude communities and the similarities and differences between the communities in Antarctica and in other regions are discussed.
Journal of Phycology 12/2013; · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We reviewed photographic images of fishes from depths of 381–2282 m in Marguerite Bay and 405–2007 m in the Amundsen Sea. Marguerite Bay fishes were 33% notothenioids and 67% non-notothenioids. Channichthyids (47%) and nototheniids (44%) were the most abundant notothenioids. The deep-living channichthyid Chionobathyscus dewitti (74%) and the nototheniid genus Trematomus (66%) were the most abundant taxa within these two families. The most abundant non-notothenioids were the macrourid Macrourus whitsoni (72%) and zoarcids (18%). Amundsen Sea fishes were 87% notothenioids and 13% non-notothenioids, the latter exclusively Macrourus whitsoni. Bathydraconids (38%) and artedidraconids (30%) were the most abundant notothenioids. We observed that Macrourus whitsoni was benthopelagic and benthic and infested by large ectoparasitic copepods. Juvenile (42 cm) Dissostichus mawsoni was not neutrally buoyant and resided on the substrate at 1277 m. Lepidonotothen squamifrons was seen near and on nests of eggs in early December. A Pogonophryne sp. from 2127 m was not a member of the deep-living unspotted P. albipinna group. Chionobathyscus dewitti inhabited the water column as well as the substrate. The pelagic zoarcid Melanostigma gelatinosum was documented in the water column a few metres above the substrate. The zoogeographic character of the Marguerite Bay fauna was West Antarctic or low-Antarctic and the Amundsen Sea was East Antarctic or high-Antarctic.
[Show abstract][Hide abstract] ABSTRACT: Plocamium cartilagineum is a common red alga on the benthos of Antarctica and can be a dominant understory species along the western Antarctic Peninsula. Algae from this region have been studied chemically, and like "P. cartilagineum" from other worldwide locations where it is common, it is rich in halogenated monoterpenes, some of which have been implicated as feeding deterrents toward sympatric algal predators. Secondary metabolites are highly variable in this alga, both qualitatively and quantitatively, leading us to probe individual plants to track the possible link of variability to genetic or other factors. Using cox1 and rbcL gene sequencing, we find that the Antarctic alga divides into two closely related phylogroups, but not species, each of which is further divided into one of five chemogroups. The chemogroups themselves, defined on the basis of Bray-Curtis similarity profiling of GC/QqQ chromatographic analyses, are largely site specific within a 10 km2 area. Thus, on the limited geographical range of this analysis, P. cartilagineum displays only modest genetic radiation, but its secondary metabolome was found to have experienced more extensive radiation. Such metabogenomic divergence demonstrated on the larger geographical scale of the Antarctic Peninsula, or perhaps even continent-wide, may contribute to the discovery of cryptic speciation.
[Show abstract][Hide abstract] ABSTRACT: Land-based aquaculture facilities often utilize additional bicarbonate sources such as commercial sea salts that are designed to boost alkalinity in order to buffer seawater against reductions in pH. Despite these preventative measures, many facilities are likely to face occasional reductions in pH and corresponding reductions in carbonate saturation states due to the accumulation of metabolic waste products. We investigated the impact of reduced carbonate saturation states (ΩCa, ΩAr) on embryonic developmental rates, larval developmental rates, and echinoplutei skeletal morphometrics in the common edible sea urchin Lytechinus variegatus under high alkalinity conditions. Commercial artificial seawater was bubbled with a mixture of air and CO2 gas to reduce the carbonate saturation state. Rates of embryonic and larval development were significantly delayed in both the low and extreme low carbonate saturation state groups relative to the control at a given time. Although symmetry of overall skeletal body lengths was not affected, allometric relationships were significantly different between treatment groups. Larvae reared under ambient conditions had significantly greater postoral arm and overall body lengths relative to body lengths than larvae grown under extreme low carbonate saturation state conditions, indicating that extreme changes in the carbonate system affected not only developmental rates but also larval skeletal shape. Reduced rates of embryonic development and delayed and altered larval skeletal growth are likely to negatively impact larval culturing of L. variegatus in land-based, intensive culture situations where calcite and aragonite saturation states are lowered by the accumulation of metabolic waste products.
[Show abstract][Hide abstract] ABSTRACT: Filamentous algal endophytes are common in many species of macroalgae along the Antarctic Peninsula, but their influence on host physiology is unknown. However, worldwide endophyte–macroalgae symbioses are known to be detrimental to vital functions of a host. The growth and survival of four Antarctic rhodophyte species were examined in situ under varying loads of endophyte infection. Growth was measured through relative growth rate and surface-area-corrected growth rate, and survivorship of individuals was documented throughout the experiment. The relationship between hosts and their endophytes was best described as innocuous in Myriogramme manginii, mildly pathogenic in Gymnogongrus turquetii and Trematocarpus antarcticus, and pathogenic in Iridaea cordata. Deterioration of thalli and decreased growth rates may be natural in the late austral summer when this experiment took place; however, the effects of increased infection probably expedited deterioration of the host. Endophytes in this study were pigmented green and brown filamentous algae, most of which are never seen as free-living thalli, and some of which may be obligate endophytes.
[Show abstract][Hide abstract] ABSTRACT: Changes in the carbonate chemistry (increased pCO2, decreased pH, and decreased carbonate saturation state) of seawater can impact the growth and physiology of echinoids and therefore, it is possible that their behavior may also be negatively affected. We investigated the impact of extreme hypercapnia on righting activity and covering response in juvenile Lytechinus variegatus (avg. diameter = 20 mm) raised in artificial seawater. Sea urchins collected from Eagle Harbor in Saint Joseph Bay, Florida (29°N, 85°W), were exposed to high pCO2 conditions, (pCO2 = 1738 ± 25.00 μatm, and pHNBS = 7.7 ± 0.002) for three months under subsatiation conditions. Righting activity (time to right to 90° position from inversion) was evaluated every three weeks and was not significantly different between treatments (repeated measures ANOVA, F = 0.84896, df = 1, 22, and p = 0.36684). At the end of the study, covering behavior (% surface area of the test covered with acrylic beads) was also not significantly different from those individuals raised under control conditions (pCO2 = 608 ± 12.00 μatm, pHNBS = 8.1 ± 0.004; and nonparametric repeated measures ANOVA, χ 2 = 1.2831, df = 1, and p = 0.25732). These results suggest that juvenile and young adult L. variegatus behavior is not altered under conditions of extreme hypercapnia. These findings are particularly relevant to future studies on the basic and applied biology of sea urchins that employ the use of artificial sea salts.
[Show abstract][Hide abstract] ABSTRACT: Most macroalgal species along the Western Antarctic Peninsula (WAP) are defended against predation, many using chemical defenses. These subtidal communities are also mostly devoid of free living filamentous algae. However, one endo/epiphyte, Elachista antarctica, is found growing exclusively out of the palatable rhodophyte Palmaria decipiens. To understand this unusual and exclusive epiphytization, we tested whether macroalgal secondary metabolites such as those responsible for deterring sympatric grazers, affect the behaviors of the epiphyte's spores. Settlement, germination, and swimming behaviors of the epiphyte's motile spores were quantified in the presence of fractionated lipophilic and hydrophilic extracts of host P. decipiens and other rhodophytes from the shallow subtidal. Host P. decipiens was the only alga tested that did not inhibit spore settlement or germination. We also examined whether extracts from these chemically rich algae affect spore swimming behaviors and found spores to be chemotactically attracted to seawater soluble extract fractions of host P. decipiens. These results indicate that chemosensory behaviors of the epiphyte's spores to metabolites associated with these chemically defended macrophytes can explain this exclusive epiphyte–host interaction.
Journal of Phycology 12/2012; 48(6). · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Echinoderms are well represented in nearshore hard-bottom (< 100 m depth) habitats along the Antarctic Peninsula where they are presumably important contributors to benthic production, carbon flow, and determinants of community structure. The present study assesses the densities of echinoderms at shallow depths (2–15 m) at five sampling sites within three kilometres of Anvers Island on the central western Antarctic Peninsula. The asteroids Odontaster validus, Granaster nutrix, Lysasterias perrieri and Adelasterias papillosa, two ophiuroids in the Amphiuridae, the holothuroids Psolicrux coatsi and Psolus carolineae and one representative of the Cucumaridae, and the regular echinoid Sterechinus neumayeri were enumerated. Mean total echinoderm densities were high (34.9 individuals m-2) and ranged from 21.9 individuals m-2 for asteroids to 2.7 individuals m-2 for holothuroids. With the exception of a positive relationship between the abundance of the regular echinoid Sterechinus neumayeri and the biomass of the brown alga Himanthothallus grandifolius, no significant relationships were found between the abundance of asteroids, ophiuroids, or holothuroids and two species of brown algae or three algal ecotypes. The present study indicates nearshore hard-bottom echinoderms are important in the carbon cycle and their inherent vulnerability to ocean acidification may have community-level impacts.
[Show abstract][Hide abstract] ABSTRACT: Detailed investigation of the Antarctic nudibranch Austrodoris kerguelenensis has resulted in the isolation of a diverse suite of new diterpenoid glyceride esters (1–16) related to the palmadorins (17–19), including one (palmadorin L (9)) that is the first halogenated diterpene from this well-studied nudibranch. Previous collections of A. kerguelenensis from McMurdo Sound, the Weddell Sea and the Western Antarctic Peninsula have afforded related diterpene glycerides, a natural product class implicated as a chemical defense in nudibranchs. In this paper we describe the isolation, structure elucidation, and stereochemical analysis of sixteen new palmadorins using a combination of one- and two-dimensional NMR techniques. Palmadorin A (17), B (18), D (1), M (10), N (11), and O (12) inhibit human erythroleukemia (HEL) cells with low micromolar IC50's, and palmadorin M inhibits Jak2, STAT5, and Erk1/2 activation in HEL cells and causes apoptosis, at 5 μM.
[Show abstract][Hide abstract] ABSTRACT: Hard bottom, subtidal communities along the Western Antarctic Peninsula are dominated by forests of large, chemically defended
macroalgae that support a very dense assemblage of amphipods. Free-living filamentous algae are rare in the subtidal, but
filamentous algal endophytes are common in many of the larger macroalgae, both likely as the result of amphipod grazing pressure.
Filamentous algae are common in the intertidal, but primarily in the upper intertidal and on high-energy shores where amphipods
are likely to be excluded much of the time. We tested the hypothesis that free-living, filamentous algae would be rapidly
consumed if transplanted from the intertidal to the subtidal, and our results clearly supported this hypothesis. The filamentous,
intertidal green alga Cladophora repens was transplanted to the benthos in 6 different macroalgal habitats. Control algae were transplanted in 3 m deeper waters
nearby (usually 12 m or less laterally) but suspended 3 m off the bottom where amphipods are absent or rare. Overall consumption
during approximately 6 h on the bottom ranged from 22 to 98% of the initial biomass, while significantly less biomass loss
occurred in the water column.
[Show abstract][Hide abstract] ABSTRACT: The marine invertebrate-derived meridianin A, the originally proposed structure for psammopemmin A, and several related 3-pyrimidylindole analogs were synthesized and subsequently investigated for central nervous system, antimalarial, and cytotoxic activity. A Suzuki coupling of an indoleborate ester to the pyrimidine electrophile was utilized to form the natural product and derivatives thereof. The 3-pyrimidineindoles were found to prevent radioligand binding to several CNS receptors and transporters, most notably, serotonin receptors (<0.2 μM K(i) for 5HT(2B)). Two compounds also inhibited the human malaria parasite Plasmodium falciparum (IC(50) <50 μM). Only the natural product was cytotoxic toward A549 cells (IC(50)=15 μM).
[Show abstract][Hide abstract] ABSTRACT: Palmerolides D-G are new bioactive macrolides isolated from the Antarctic tunicate Synoicum adareanum and are related to the melanoma-selective cytotoxin palmerolide A. Most of these palmerolides are potent V-ATPase inhibitors and have sub-micromolar activity against melanoma. Though palmerolide A remains the most potent of this series of natural products against mammalian V-ATPase, recent data suggests that palmerolide D is the most potent against melanoma. A comparison of the bioactivity data obtained for these natural product palmerolides has provided insight into the substructures necessary to retain V-ATPase inhibition and cytotoxic activity.