ALBERT

Description: Marine environments are influenced by a wide diversity of anthropogenic and natural substances and organisms that may have adverse effects on human health and ecosystems. Real-time measurements of pollutants, toxins, and pathogens across a range of spatial scales are required to adequately monitor these hazards, manage the consequences, and to understand the processes governing their magnitude and distribution. Significant technological advancements have been made in recent years for the detection and analysis of such marine hazards. In particular, sensors deployed on a variety of mobile and fixed-point observing platforms provide a valuable means to assess hazards. In this review, we present state-of-the-art of sensor technology for the detection of harmful substances and organisms in the ocean. Sensors are classified by their adaptability to various platforms, addressing large, intermediate, or small areal scales. Current gaps and future demands are identified with an indication of the urgent need for new sensors to detect marine hazards at all scales in autonomous real-time mode. Progress in sensor technology is expected to depend on the development of small-scale sensor technologies with a high sensitivity and specificity towards target analytes or organisms. However, deployable systems must comply with platform requirements as these interconnect the three areal scales. Future developments will include the integration of existing methods into complex and operational sensing systems for a comprehensive strategy for long-term monitoring.

Description: We compare and contrast the ecological impacts of atmospheric and oceanic circulation patterns on polar and sub-polar marine ecosystems. Circulation patterns differ strikingly between the north and south. Meridional circulation in the north provides connections between the sub-Arctic and Arctic despite the presence of encircling continental landmasses, whereas annular circulation patterns in the south tend to isolate Antarctic surface waters from those in the north. These differences influence fundamental aspects of the polar ecosystems from the amount, thickness and duration of sea ice, to the types of organisms, and the ecology of zooplankton, fish, seabirds and marine mammals. Meridional flows in both the North Pacific and the North Atlantic oceans transport heat, nutrients, and plankton northward into the Chukchi Sea, the Barents Sea, and the seas off the west coast of Greenland. In the North Atlantic, the advected heat warms the waters of the southern Barents Sea and, with advected nutrients and plankton, supports immense biomasses of fish, seabirds and marine mammals. On the Pacific side of the Arctic, cold waters flowing northward across the northern Bering and Chukchi seas during winter and spring limit the ability of boreal fish species to take advantage of high seasonal production there. Southward flow of cold Arctic waters into sub-Arctic regions of the North Atlantic occurs mainly through Fram Strait with less through the Barents Sea and the Canadian Archipelago. In the Pacific, the transport of Arctic waters and plankton southward through Bering Strait is minimal. In the Southern Ocean, the Antarctic Circumpolar Current and its associated fronts are barriers to the southward dispersal of plankton and pelagic fishes from sub-Antarctic waters, with the consequent evolution of Antarctic zooplankton and fish species largely occurring in isolation from those to the north. The Antarctic Circumpolar Current also disperses biota throughout the Southern Ocean, and as a result, the biota tends to be similar within a given broad latitudinal band. South of the Southern Boundary of the ACC, there is a large-scale divergence that brings nutrient-rich water to the surface. This divergence, along with more localized upwelling regions and deep vertical convection in winter, generates elevated nutrient levels throughout the Antarctic at the end of austral winter. However, such elevated nutrient levels do not support elevated phytoplankton productivity through the entire Southern Ocean, as iron concentrations are rapidly removed to limiting levels by spring blooms in deep waters. However, coastal regions, with the upward mixing of iron, maintain greatly enhanced rates of production, especially in coastal polynyas. In these coastal areas, elevated primary production supports large biomasses of zooplankton, fish, seabirds, and mammals. As climate warming affects these advective processes and their heat content, there will likely be major changes in the distribution and abundance of polar biota, in particular the biota dependent on sea ice.

Description: We used a top–down, multidisciplinary approach to examine the physical and biological environment of the pack ice of the eastern Ross Sea (approximately 125–170°W) during the austral summer of 1999/2000 from RVIB Nathaniel B. Palmer and its ship-based helicopters. The approach focused on pack-ice seals while incorporating studies of biotic and abiotic factors that may influence the distribution and abundances of these apex predators in the Ross Sea to yield a holistic understanding of the structure and function of this complex, large marine ecosystem. This research represented the US component of the international Antarctic Pack Ice Seal (APIS) program, which was designed to document the circumpolar distribution and abundance of Antarctic pack-ice seals. The eastern Ross Sea is one of the two major areas in the Southern Ocean where substantial pack ice exists throughout summer. We found that vast multi-year ice floes (〉20 km diameter) and smaller floes north of the shore-fast ice front provide a unique habitat for seals and penguins (apex predators) to forage and haul out while molting in late summer. Farther north, more Ross seals were observed than in any previous surveys in the circumpolar pack ice, perhaps because they are attracted to the area in summer to molt on large stable first-year ice floes. Extensive fast ice along the coastline and drifting pack ice in the shelf–slope boundary zone provided haul-out areas for seals and penguins with access to feeding in the coastal shelf region. Distributions of potential prey for seals and penguins varied over the study area, as determined by nets, acoustics, and diving surveys. Antarctic krill (Euphausia superba) were found throughout the survey region, overlapping the distributions of two smaller species, Thysanoëssa macrura (primarily off-shelf) and E. crystallorophias (primarily found on-shelf). In some locations, E. superba occurred at high densities underneath ice floes, where they foraged on the sea-ice microbial community. Two general fish communities, oceanic and shelf, were distinguished. Off-shelf fishes were members of the classic oceanic midwater fish fauna, whereas on-shelf fishes were Antarctic endemics. The abundance of pelagic fishes was relatively low throughout the study area compared with other Southern Ocean ecosystems. In contrast, benthic fish biomass and diversity on-shelf were high (41 species, 6 families). Hydroacoustic analyses indicated that densities of potential prey were highest in the coastal shelf region where large aggregations of euphausiids (primarily E. crystallorophias) and individual juvenile Antarctic silverfish (Pleuragramma antarcticum) occurred.

Description: The C:N ratio is a critical parameter used in both global ocean carbon models and field studies to understand carbon and nutrient cycling as well as to estimate exported carbon from the euphotic zone. The so-called Redfield ratio (C:N = 6.6 by atoms) [Redfield et al., 1963] is widely used for such calculations. Here we present data from the NE Greenland continental shelf that show that most of the C:N ratios for particulate (autotrophic and heterotrophic) and dissolved pools and rates of transformation among them exceed Redfield proportions from June to August, owing to species composition, size, and biological interactions. The ecosystem components that likely comprised sinking particles and had relatively high C:N ratios (geometric means) included (1) the particulate organic matter (C:N = 8.9) dominated by nutrient-deficient diatoms, resulting from low initial nitrate concentrations (approximately 4 μM) in Arctic surface waters; (2) the dominant zooplankton, herbivorous copepods (C:N = 9.6), having lipid storage typical of Arctic copepods; and (3) copepod fecal pellets (C:N = 33.2). Relatively high dissolved organic carbon concentrations (median 105 μM) were approximately 25 to 45 μM higher than reported for other systems and may be broadly characteristic of Arctic waters. A carbon-rich dissolved organic carbon pool also was generated during summer. Since the magnitude of carbon and nitrogen uncoupling in the surface mixed layer appeared to be greater than in other regions and occurred throughout the productive season, the C:N ratio of particulate organic matter may be a better conversion factor than the Redfield ratio to estimate carbon export for broad application in northern high-latitude systems.

Description: There are various similarities and differences in zooplankton processes between Arctic Ocean (AO) and Southern Ocean (SO) polynyas, many of which are due to fundamental differences in their respective ecosystem properties. The composition of zooplankton communities in AO and SO polynyas is largely dependent upon advection from local, ice-covered waters, with little evidence of an endemic, polynya zooplankton fauna. While copepods are common in both systems, a major difference is the predominance of euphausiids in the SO and appendicularian tunicates in the AO. The same genera of small copepods occur in both the AO and SO and appear to derive little benefit from the higher primary productivity and extended growing season of polynyas. In contrast, larger calanoid copepods appear to derive recruitment and life cycle benefits from the diatom production and heat in polynyas, with higher egg production rates and shorter generation times. Most large calanoid copepods overwinter in diapause in AO polynyas, while some proportion of SO populations remain in surface waters. Grazing impact by copepods in AO polynyas accounts for about 20% of primary productivity d−1, with appendicularian tunicates accounting for another 20% d−1. The few estimates of community impact in the SO are variable. In both regions, individual zooplankton feeding rates are high and equivalent to boreal ocean values; thus, grazing impact depends primarily on the biomass of zooplankton and phytoplankton. SO zooplankton contribute to the vertical particulate flux through faecal pellets from euphausiids, copepods and pteropods, while the contribution in AO polynyas is primarily through appendicularian tunicate faecal pellets and shed houses and copepod faeces. Maximum pellet flux in both the AO and SO occurs at times of high biomass of diatoms. The primary benefits of polar polynyas to zooplankton processes results from the greater production of diatoms and extended productive period, with few differences in individual daily rations or food web transfer efficiencies relative to temperate and boreal systems.