Water temperature measured in Independence Bay, Pisco, Peru

Independencia Bay can be considered as one of the most productive invertebratc fishing grounds worldwide. One of the most important exploited species is the scallop (Argopecten purpuratus) with strong catching fluctuations related to El Nino and La Nina events and to inadequate Management strategies. During strong warming periods annual landings reach up to 50000 t in an area of about 150 km**2 and during cold years they remain around 500 to 1000 t. This study analyses the changes in scallop landings at Independencia Bay observed during the last two decades and discusses the main factors affecting the scallop proliferations during the EI Nino events. In this way data on landings, sea surface temperature and those related to growth, reproduction, predation, mean density and oxygen concentration from published and unpublished Papers are used. The relationship between annual catches and average water temperature over the preceding reproductive period of the scallop over the past 20 year's period, showed that scallop production is affected positively only with strong EI Nino such as those of 1983 and 1998. Our review showed that the scallop stock proliferation can be traced to the combined effect of (1) an increase in reproductive output through an acceleration of gonad maturation and a higher spawning frequency; (2) a shortening of the larval period and an increase in larval survival; (3) an increase in the individual growth performance; (4) an increase in the juvenile and adult survival through reduction of predator biomass; (5) an increase in carrying capacity of the scallop banks due to elevated oxygen levels.

Data from PhD thesis

The ocean quahog, Arctica islandica is the longest-lived non-colonial animal known to science. A maximum individual age of this bivalve of 405 years has been found in a population off the north western coast of Iceland. Conspicuously shorter maximum lifespan potentials (MLSPs) were recorded from other populations of A. islandica in European waters (e.g. Kiel Bay: 30 years, German Bight: 150 years) which experience wider temperature and salinity fluctuations than the clams from Iceland. The aim of my thesis was to identify possible life-prolonging physiological strategies in A. islandica and to examine the modulating effects of extrinsic factors (e.g. seawater temperature, food availability) and intrinsic factors (e.g. species-specific behavior) on these strategies. Burrowing behavior and metabolic rate depression (MRD), tissue-specific antioxidant and anaerobic capacities as well as cell-turnover (= apoptosis and proliferation) rates were investigated in A. islandica from Iceland and the German Bight. An inter-species comparison of the quahog with the epibenthic scallop Aequipecten opercularis (MLSP = 8-10 years) was carried out in order to determine whether bivalves with short lifespans and different lifestyles also feature a different pattern in cellular maintenance and repair. The combined effects of a low-metabolic lifestyle, low oxidative damage accumulation, and constant investment into cellular protection and tissue maintenance, appear to slow-down the process of physiological aging in A. islandica and to afford the extraordinarily long MLSP in this species. Standard metabolic rates were lower in A. islandica when compared to the shorter-lived A. opercularis. Furthermore, A. islandica regulate mantle cavity water PO2 to mean values < 5 kPa, a PO2 at which the formation of reactive oxygen species (ROS) in isolated gill tissues of the clams was found to be 10 times lower than at normoxic conditions (21 kPa). Burrowing and metabolic rate depression (MRD) in Icelandic specimens were more pronounced in winter, possibly supported by low seawater temperature and food availability, and seem to be key energy-saving and life-prolonging parameters in A. islandica. The signaling molecule nitric oxide (NO) may play an important role during the onset of MRD in the ocean quahog by directly inhibiting cytochome-c-oxidase at low internal oxygenation upon shell closure. In laboratory experiments, respiration of isolated A. islandica gills was completely inhibited by chemically produced NO at low experimental PO2 <= 10 kPa. During shell closure, mantle cavity water PO2 decreased to 0 kPa for longer than 24 h, a state in which ROS production is supposed to subside. Compared to other mollusk species, onset of anaerobic metabolism is late in A. islandica in the metabolically reduced state. Increased accumulation of the anaerobic metabolite succinate was initially detected in the adductor muscle of the clams after 3.5 days under anoxic incubation or in burrowed specimens. A ROS-burst was absent in isolated gill tissue of the clams following hypoxia (5 kPa)-reoxygenation (21 kPa). Accordingly, neither the activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), nor the specific content of the ROS-scavenger glutathione (GSH) was enhanced in different tissues of the ocean quahog after 3.5 days of self-induced or forced hypoxia/anoxia to prepare for an oxidative burst. While reduced ROS formation compared to routine levels lowers oxidative stress during MRD and also during surfacing, the general preservation of high cellular defense and the efficient removal and replacement of damaged cells over lifetime seem to be of crucial importance in decelerating the senescent decline in tissues of A. islandica. Along with stable antioxidant protection over 200 years of age, proliferation rates and apoptosis intensities in most investigated tissues of the ocean quahog were low, but constant over 140 years of age. Accordingly, age-dependent accumulations of protein and lipid oxidation products are lower in A. islandica tissues when compared to the shorter-lived bivalve A. opercularis. The short-lived swimming scallop is a model bivalve species representing the opposite life and aging strategy to A. islandica. In this species permanently high energy throughput, reduced investment into antioxidant defense with age, and higher accumulation of oxidation products are met by higher cell turnover rates than in the ocean quahog. The only symptoms of physiological change over age ever found in A. islandica were decreasing cell turnover rates in the heart muscle over a lifetime of 140 years. This may either indicate higher damage levels and possibly ongoing loss of functioning in the heart of aging clams, or, the opposite, lower rates of cell damage and a reduced need for cell renewal in the heart tissue of A. islandica over lifetime. Basic physiological capacities of different A. islandica populations, measured at controlled laboratory conditions, could not explain considerable discrepancies in population specific MLSPs. For example, levels of tissue-specific antioxidant capacities and cell turnover rates were similarly high in individuals from the German Bight and from Iceland. Rather than genetic differences, the local impacts of environmental conditions on behavioral and physiological traits in the ocean quahog seem to be responsible for differences in population-specific MLSPs.

Stable isotopic ratios, shell lengths and organochlorine compounds in four bivalve species collected in July 2009 around Svalbard

Organochlorine compounds (OC) were determined in Arctic bivalves (Mya truncata, Serripes groenlan-dicus, Hiatella arctica and Chlamys islandica) from Svalbard with regard to differences in geographic location, species and variations related to their size and age. Higher chlorinated polychlorinated biphenyls (PCB 101-PCB 194), chlordanes and alpha-hexachlorocyclohexane (alpha-HCH) were consistently detected in the bivalves and PCBs dominated the OC load in the organisms. OC concentrations were highest in Mya truncata and the lowest in Serripes groenlandicus. Species-specific OC levels were likely related to differences in the species' food source, as indicated by the d13C results, rather than size and age. Higher OC concentrations were observed in bivalves from Kongsfjorden compared to the northern sampling locations Liefdefjorden and Sjuoyane. The spatial differences might be related to different water masses influencing Kongsfjorden (Atlantic) and the northern locations (Arctic), with differing phytoplankton bloom situations.

Benthos fauna in the North Sea from 2 surveys in 1986 and 1987

During two surveys in the North Sea, in summer 1986 and in winter 1987, larger epibenthos was collected with a 2 m beam trawl. The distributions of the species were checked for average linkage by means of the JACCARD-index cluster analysis. In summer two main clusters can be recognized. These are situated to the north and to the south of the Dogger Bank. In winter two main clusters may be recognized as well, but these clusters divide the North Sea into a western and an eastern part. We conclude, that these differences of epibenthos characteristics are correlated with seasonal changes in water body distributions.

Glacial-interglacial record of ODP Site 181-1119 in the Canterbury Bright, Southwest Pacific Ocean

Ocean Drilling Program (ODP) Site 1119 is located at water depth 395 m near the subtropical front (STF; here represented by the Southland Front), just downslope from the shelf edge of eastern South Island, New Zealand. The upper 86.19 metres composite depth (mcd) of Site 1119 sediment was deposited at an average sedimentation rate of 34 cm/kyr during Marine Isotope Stages (MIS) 1-8 (0-252 ka), and is underlain across a ~25 kyr intra-MIS 8 unconformity by MIS 8.5-11 (277-367 ka) and older sediment deposited at ~14 cm/kyr. A time scale is assigned to Site 1119 using radiocarbon dates for the period back to ~39 ka, and, prior to then, by matching its climatic record with that of the Vostok ice core, which it closely resembles. Four palaeoceanographic proxy measures for surface water masses vary together with the sandy-muddy, glacial-interglacial (G/I) cyclicity at the site. Interglacial intervals are characterised by heavy delta13C, high colour reflectance (a proxy for carbonate content), low Q-ray (a proxy for clay content) and light delta18O; conversely, glacial intervals exhibit light delta13C, low reflectance, high Q-ray and heavy delta18O signatures. Early interglacial intervals are represented by silty clays with 10-105-cm-thick beds of sharp-based (Chondrites-burrowed), shelly, graded, fine sand. The sands are rich in foraminifera, and were deposited distant from the shoreline under the influence of longitudinal flow in relatively deep water. Glacial intervals comprise mostly micaceous silty clay, though with some thin (2-10 cm thick) sands present also at peak cold periods, and contain the cold-water scallop Zygochlamys delicatula. Interglacial sandy intervals are characterised by relatively low sedimentation rates of 5-32 cm/kyr; cold climate intervals MIS 10, 6 and 2 have successively higher sedimentation rates of 45, 69 and 140 cm/kyr. Counter-intuitively,and forced by the bathymetric control of a laterally-moving shoreline during G/I and I/G transitions, the 1119 core records a southeasterly (seaward) movement of the STF during early glacial periods, accompanied by the incursion of subtropical water (STW) above the site, and northwesterly (landward) movement during late glacial and interglacial times, resulting in a dominant influence then of subantarctic surface water (SAW). The history of passage of these different water masses at the site is clearly delineated by their characteristic delta13C values. The intervals of thin, graded sands-muds which occur within MIS 2-3, 6, 7.4 and 10 indicate the onset at times of peak cold of intermittent bottom currents caused by strengthened and expanded frontal flows along the STF, which at such times lay near Site 1119 in close proximity to seaward-encroaching subantarctic waters within the Bounty gyre. In common with other nearby Southern Hemisphere records, the cold period which represents the last glacial maximum lasted between ~23-18 ka at Site 1119, during which time the STF and Subantarctic Front (SAF) probably merged into a single intense frontal zone around the head of the adjacent Bounty Trough.

Model parameter

Interannual environmental variability in Peru is dominated by the El Niño Southern Oscillation (ENSO). The most dramatic changes are associated with the warm El Niño (EN) phase (opposite the cold La Niña phase), which disrupts the normal coastal upwelling and affects the dynamics of many coastal marine and terrestrial resources. This study presents a trophic model for Sechura Bay, located at the northern extension of the Peruvian upwelling system, where ENSO-induced environmental variability is most extreme. Using an initial steady-state model for the year 1996, we explore the dynamics of the ecosystem through the year 2003 (including the strong EN of 1997/98 and the weaker EN of 2002/03). Based on support from literature, we force biomass of several non-trophically-mediated 'drivers' (e.g. Scallops, Benthic detritivores, Octopus, and Littoral fish) to observe whether the fit between historical and simulated changes (by the trophic model) is improved. The results indicate that the Sechura Bay Ecosystem is a relatively inefficient system from a community energetics point of view, likely due to the periodic perturbations of ENSO. A combination of high system productivity and low trophic level target species of invertebrates (i.e. scallops) and fish (i.e. anchoveta) results in high catches and an efficient fishery. The importance of environmental drivers is suggested, given the relatively small improvements in the fit of the simulation with the addition of trophic drivers on remaining functional groups' dynamics. An additional multivariate regression model is presented for the scallop Argopecten purpuratus, which demonstrates a significant correlation between both spawning stock size and riverine discharge-mediated mortality on catch levels. These results are discussed in the context of the appropriateness of trophodynamic modeling in relatively open systems, and how management strategies may be focused given the highly environmentally influenced marine resources of the region.

Soft-bottom macrobenthic faunal associations in the southern Chilean glacial fjord complex

Macrobenthic associations were investigated at 29 sampling stations with a semi-quantitative Agassiz trawl, ranging from the South Patagonian Icefield to the Straits of Magellan in the South Chilean fjord system. A total of 1,895 individuals belonging to 131 species were collected. 19 species belong to colonial organisms, mainly Bryozoa (17 species) and Octocorallia (2 species). The phylum Echinodermata was the most diverse in species number (47 species), with asteroids (25 species) and ophiuroids (13 species) being the best represented within this taxon. Polychaeta was the second dominant group in terms of species richness (46 species). Multidimensional scaling ordination (MDS) separated two station groups, one related to fjords and channels off the South Patagonian Icefield and the second one to stations surrounding the Straits of Magellan. 45 species account for 90% of the dissimilarity between these two groups. These differences can mainly be explained by the influence of local environmental conditions determined by processes closely related to the pres- ence/absence of glaciers. Abiotic parameters such as water depth, type of sediment and chemical features of the superficial sediment were not correlated with the numbers of individuals caught by the Agassiz trawl in each group of sampling stations.