Rita A. Horner

Ecology of sea ice biota - 2. Global significance

SummaryThe sea ice does not only determine the ecology of ice biota, but it also influences the pelagic systems under the ice cover and at ice edges. In this paper, new estimates of Arctic and Antarctic production of biogenic carbon are derived, and differences as well as similarities between the two oceans are examined. In ice-covered seas, high algal concentrations (blooms) occur in association with several types of conditions. Blooms often lead to high sedimentation of intact cells and faecal pellets. In addition to ice-related blooms, there is progressive accumulation of organic matter in Arctic multi-year ice, whose fate may potentially be similar to that of blooms. A fraction of the carbon fixed by microalgae that grow in sea ice or in relation to it is exported out of the production zone. This includes particulate material sinking out of the euphotic zone, and also material passed on to the food web. Pathways through which ice algal production does reach various components of the pelagic and benthic food webs, and through them such top predators as marine mammals and birds, are discussed. Concerning global climate change and biogeochemical fluxes of carbon, not all export pathways from the euphotic zone result in the sequestration of carbon for periods of hundreds of years or more. This is because various processes, that take place in both the ice and the water column, contribute to mineralize organic carbon into CO2 before it becomes sequestered. Processes that favour the production and accumulation of biogenic carbon as well as its export to deep waters and sequestration are discussed, together with those that influence mineralization in the upper ice-covered ocean.

Ecology of sea ice biota

SummaryPolar regions are covered by extensive sea ice that is inhabited by a variety of plants and animals. The environments where the organisms live vary depending on the structure and age of the ice. Many terms have been used to describe the habitats and the organisms. We here characterize the habitats and communities and suggest some standard terms for them. We also suggest routine sampling methods and reporting units for measurements of biological and chemical variables.

Ecology of sea ice biota - 1. Habitat, terminology, and methodology

SummaryPolar regions are covered by extensive sea ice that is inhabited by a variety of plants and animals. The environments where the organisms live vary depending on the structure and age of the ice. Many terms have been used to describe the habitats and the organisms. We here characterize the habitats and communities and suggest some standard terms for them. We also suggest routine sampling methods and reporting units for measurements of biological and chemical variables.

Microalgae on the arctic ocean section, 1994: species abundance and biomass

Algal species from the ice, the water directly below the ice (the sub-ice area), and the water column from 21 stations in the Arctic Ocean were examined using epifluorescence and inverted light microscopy. Biomass of autotrophic dinoflagellates and other miscellaneous autotrophic flagellates was determined for the first time in the central Arctic basins. Together these two groups dominated phytoplankton biomass in 74% of samples from the central Arctic, with diatom biomass predominant in the remainder. Picophytoplankton at selected stations in the Canada and Makarov Basins contributed 93% to autotroph cell numbers and 36% to autotroph biomass. Diatom species achieved high biomass in ice and sub-ice samples. The centric diatom Melosira arctica dominated the sub-ice area, while pennate diatoms were major contributors to the ice samples. Despite ample silicate concentrations in the water, diatom frustules were often lightly silicified.

Proposed terminology and reporting units for sea ice algal assemblages

SummaryMany terms and units are used to describe the algae associated with sea ice. Most of these terms are open to misinterpretation and have been frequently misused. The use of a number of different units when reporting on experimental studies makes it difficul, if not impossible, to compare studies done by different investigators. In an attempt to avoid these ambiguities and to make comparisons easier, we here suggest some standard terms and repoting units that should be used when discussing ice algal assemblages.

Use of Phytoplankton Species Indicators to Track the Origin of Phytoplankton Blooms in Willapa Bay, Washington

We focus on the question of whether high phytoplankton production events observed in a United States Pacific Northwest estuary consist of estuarine species blooms fueled by oceanic nutrient input or reflect offshore oceanic blooms that have advected into the estuary. Our approach is to use certain phytoplankton species as indicators associated with water mass origin, either estuarine or oceanic, to help resolve this question in Willapa Bay, Washington. We used species analysis and primary production data from 10 selected dates in May–September of 1998 and 1999, representing periods of high through low productivity. Out of 108 phytoplankton species identified from Willapa Bay, nine were selected and tested as indicators of oceanic species, six as estuarine, and two as surf zone. Our test results demonstrated the oceanic and estuarine species to be satifactory indicators of source waters. The prevalence of these species indicators in our samples revealed that the highest primary production and the appearance ofPseudo-nitzschia spp. were associated with oceanic intrusions of phytoplankton biomass into Willapa Bay. While the largest blooms were oceanic in origin, numerous medium-sized production events were from either oceanic, surf zone, or estuarine sources, indicating a complex situation.

An Alexandrium Spp. Cyst Record from Sequim Bay, Washington State, USA, and its Relation to Past Climate Variability1

Since the 1970s, Puget Sound, Washington State, USA, has experienced an increase in detections of paralytic shellfish toxins (PSTs) in shellfish due to blooms of the harmful dinoflagellate Alexandrium. Natural patterns of climate variability, such as the Pacific Decadal Oscillation (PDO), and changes in local environmental factors, such as sea surface temperature (SST) and air temperature, have been linked to the observed increase in PSTs. However, the lack of observations of PSTs in shellfish prior to the 1950s has inhibited statistical assessments of longer‐term trends in climate and environmental conditions on Alexandrium blooms. After a bloom, Alexandrium cells can enter a dormant cyst stage, which settles on the seafloor and then becomes entrained into the sedimentary record. In this study, we created a record of Alexandrium spp. cysts from a sediment core obtained from Sequim Bay, Puget Sound. Cyst abundances ranged from 0 to 400 cysts · cm−3 and were detected down‐core to a depth of 100 cm, indicating that Alexandrium has been present in Sequim Bay since at least the late 1800s. The cyst record allowed us to statistically examine relationships with available environmental parameters over the past century. Local air temperature and sea surface temperature were positively and significantly correlated with cyst abundances from the late 1800s to 2005; no significant relationship was found between PDO and cyst abundances. This finding suggests that local environmental variations more strongly influence Alexandrium population dynamics in Puget Sound when compared to large‐scale changes.

Toxic diatoms: report on a workshop

A workshop on toxic diatoms held during the 12th International Diatom Symposium, Renesse, The Netherlands, attracted about 25 people from 10 countries. The purpose of the workshop was to make diatomists aware that some diatoms produce toxins that can cause human health problems.

Gotthilf and Irmtraut Hempel (eds): Biological Studies in Polar Oceans: Exploration of Life in Icy Waters

This book, designed primarily for students and teachers, is a welcome addition to the literature on polar seas. It describes, in layman’s terms, the biology and environmental features that affect the biology of these very important parts of the world ocean. It is an updated version in English of a similar work published 15 years ago in German that was also edited by the Hempels. It includes 35, mostly short, research reports and reviews written by leading scientists and students, mostly Germans working on RV Polarstern and describes the considerable knowledge gained in these once forbidding regions. The book is divided into eight parts based on the physical environment, the various kinds of organisms living in this environment, and biogeochemical cycling plus sections on polar biology in a changing world and thoughts about the future. The first part of the book, called Framework, has overview papers on the physical oceanography of both the Arctic and Antarctic and a brief description of the geologic history of polar oceans including ice presence and absence. Part two deals with the sea ice, how it is formed and its seasonal cycle, and the organisms living in it and how they are able to sustain life in this unusual environment. A sidebar describes coupling between the ice and the underlying water column. Part three discusses the phytoplankton and protozooplankton (one paper) and zooplankton (seven papers). The first paper discusses the single-celled organisms, their seasonal cycle, growth, feeding modes, and the factors that limit their production including ice, nutrients, temperature (warming), and acidification. The zooplankton papers describe differences between the Arctic and Antarctic with regard to abundance, distribution, life cycle strategies, composition, diversity, and size and how these are related to local environmental conditions. Three papers are devoted to the Antarctic krill, their distribution, abundance, population dynamics, overwintering physiology, and growth. Part four moves to the sea floor and is a mixed bag of information about the benthos starting with myths and facts including such topics as perturbation, diversity, benthic decapods, recruitment, size, age, presence of pelagic larvae, and life cycles related to seasonality, all in the Antarctic. The Arctic paper has Glasnost and Global Change in its title and has information on those topics as well as the bottom communities, pelagic-benthic coupling, and benthic species richness. The Antarctic paper deals with the deep ocean and the Amundsen Sea. One paper discusses the ancient and little known group, Priapulida. I was impressed that the largest species is sometimes abundant enough to provide a major food supply to Alaskan walruses. The final paper is about seaweeds from Spitsbergen and King George Island, Antarctica, with information on seasonal development, temperature, light, and affect of increased UV-B radiation. Part five gets to the top organisms with topics ranging from fish, to cephalopods, to penguins, seals, whales, krill fishing, and humans. The dominant fish species, out of approximately 200, is the Antarctic silverfish, Pleuragramma antarcticum, a bottom-dweller that has learned to swim, is able to graze on all sizes of zooplankton, and are then eaten by birds, seals, squids, and whales. Of the cephalopods in the Antarctic, there are only a few squid species, while the octopods are more diverse. Emperor penguins, the only birds breeding during the Antarctic winter, are excellent divers allowing them to forage throughout the water column, even in winter when they R. A. Horner (&) University of Washington, Seattle, USA e-mail: rita@ocean.washington.edu