The effects of manipulation of sedimentary iron and organic matter on sediment biogeochemistry and seagrasses in a subtropical carbonate environment

The microbial metabolism of organic matter (OM) in seagrass beds can create sulfidic conditions detrimental to seagrass growth; iron (Fe) potentially has ameliorating effects through titration of the sulfides and the precipitation of iron-sulfide minerals into the sediment. In this study, the biogeochemical effects of Fe availability and its interplay with sulfur and OM on sulfide toxicity, phosphorous (P) availability, seagrass growth and community structure were tested. The availability of Fe and OM was manipulated in a 2 × 2 factorial experiment arranged in a Latin square, with four replicates per treatment. The treatments included the addition of Fe, the addition of OM, the addition of both Fe and OM as well as no addition. The experiment was conducted in an oligotrophic, iron-deficient seagrass bed. Fe had an 84.5% retention efficiency in the sediments with the concentration of Fe increasing in the seagrass leaves over the course of the experiment. Porewater chemistry was significantly altered with a dramatic decrease in sulfide levels in Fe addition plots while sulfide levels increased in the OM addition treatments. Phosphorus increased in seagrass leaves collected in the Fe addition plots. Decreased sulfide stress was evidenced by heavier δ³⁴S in leaves and rhizomes from plots to which Fe was added. The OM addition negatively affected seagrass growth but increased P availability; the reduced sulfide stress in Fe added plots resulted in elevated productivity. Fe availability may be an important determinant of the impact that OM has on seagrass vitality in carbonate sediments vegetated with seagrasses.     

Body size and area‐incidence relationships: is there a general pattern?

Aim This paper tests firstly for the existence of a general relationship between body size of terrestrial animals and their incidence across habitat patches of increasing size, and secondly for differences in this relationship between insects and vertebrates. Location The analysis was based on the occupancy pattern of 50 species from 15 different landscapes in a variety of ecosystems ranging from Central European grassland to Asian tropical forest. Methods The area‐occupancy relationship was described by incidence functions that were calculated using logistic regression. A correlation analysis between body size of the species and the patch area referring to the two given points of the incidence function was performed. In order to test for an effect of taxon (insects vs. vertebrates), an analysis of covariance was conducted. Results In all species, the incidence was found to increase with increasing patch area. The macroecological analysis showed a significant relationship between the incidence in habitat patches and the body size of terrestrial animals. The area requirement was found to increase linearly with increasing body size on a log‐log scale. This relationship did not differ significantly between insects and vertebrates. Conclusions The approach highlighted in this paper is to associate incidence functions with body size. The results suggest that body size is a general but rather rough predictor for the area requirements of animals. The relationship seems valid for a wide range of body sizes of terrestrial animals. However, further studies including isolation of habitats as well as additional species traits into the macroecological analysis of incidence functions are needed.     

Seasonal growth of Atlantic cod: effects of temperature, feeding and reproduction

Growth of 2659 Atlantic cod Gadus morhua aged 4 to 9 years examined in Placentia Bay, Newfoundland, peaked in most cases in June and was at a minimum in October or November. Water temperature, partial fullness index ( I _P) and gonado‐somatic index ( I _G) explained between 31 and 52% of the monthly variability in growth. Temperature and I _P of capelin Mallotus villosus had significant effects on growth of all age groups and explained most of the variance for ages 6–8 and 4–5 years, respectively. The I _P of large invertebrates (ages 4 to 7 years), sandlance ( Ammodytes sp. age 6 years) and demersal fishes (age 9 years) had age‐specific effects in the model. Overall, amphipods, decapods and echinoderms dominated the Atlantic cod diet in most seasons, but fish consumption by Atlantic cod was high in June and July, particularly on capelin. The rapid increase in somatic mass during June and July occurred despite cold water temperatures ( < 3° C at 50 m) and moderate to high gonado‐somatic index. The findings of this study suggest that when food was not a limiting factor, growth tended to increase even when Atlantic cod occupied colder waters, but when food was limiting, the opposite may have occured.     

Reflections on the Conservation and Sustainable Use of Genetic Resources in the Deep Seabed Beyond the Limits of National Jurisdiction

Attention is increasingly being given to genetic resources in the deep seabed beyond the limits of national jurisdiction owing to their considerable potential scientific and economic value. At the same time, there are concerns that the increased demand for these genetic resources may result in their unsustainable collection or even in the extinction of species in the deep seabed. At present there is no specific legal framework governing these resources in international law. Thus, this article explores the relevant rules of international law applicable to the conservation and sustainable use of genetic resources in the deep seabed.     

ULTRASTRUCTURE AND ECOLOGY OF AUREOCOCCUS ANOPHAGEFERENS GEN. ET SP. NOV. (CHRYSOPHYCEAE): THE DOMINANT PICOPLANKTER DURING A BLOOM IN NARRAGANSETT BAY,RHODE ISLAND,SUMMER 19851

Observations of a marked cessation of feeding in filter feeding animals maintained in flowing Narragansett Bay seawater in June 1985 drew our attention to a bloom of a golden alga 2 μm in diameter at unprecedented populations of 10⁹ cells. L^?1. This picoplankter lacked morphological features useful in discriminating it from other similar sized forms with either phase contrast or epifluorescence light microscopy. Natural populations of picoplankton, obtained from the height of the bloom until its decline, were examined in thin section with transmission electron microscopy. A cell with a single chloroplast, nucleus, and mitochondrion and an unusual exocellular polysaccharide-like layer was apparently the bloom alga. The ultrastructure of this alga is consistent with that of the Chrysophyceae, and a new genus and species, Aureococcus anophagefferens is described. Attempts to grow this previously unrecognized picoplanktonic alga as an obligate phototroph failed and only yielded cultures of other previously described picoalgae. Facultative and obligate phagotrophic protists with ingested cells of Aureococcus were only observed as the bloom waned and minute diatoms became common. Cells of A. anophagefferens with virus particles typical for picoalgae occurred throughout the bloom. Populations of the usually dominant photosynthetic picoplankter, the cyanobacterium Synechococcus Nägeli, were depressed during the bloom. This could be due in part to selective grazing on Synechococcus rather than Aureococcus by elevated populations of Calycomonas ovalis Wulff which accompanied the algal bloom.     

Nutrient release rates from the sediments of Saginaw Bay,Lake Huron

Direct measurements of net production rates and pore water profiles of solutes in the fine-grained sediments of Saginaw Bay, imply corresponding steady-state fluxes to the overlying water of 1.1–1.3 (I), 450–1010 (NH₄ ⁺), 1250–2650 (Si(OH)₄), 3000–3400 (Ca²⁺), 440–1330 (Mg²⁺), 1.5–728 (Fe²⁺), and 179–281 (Mn²⁺) moles/m²/day and 11.0–11.8 (alkalinity) meq/m²/day at 17.5 °C. Silica production rates in sediments apparently follow first order kinetics with a rate coefficient of 0.09/day and a steady-state silica concentration of 1.2 mM at 23.5°C. The remaining solutes follow kinetics approximately independent of solute concentration over the range of concentrations observed. Measured solute production rates are consistent with observed solute profiles only if lateral diffusion gradients are maintained in the sediments by the burrowing and irrigation activity of benthic organisms such asChironomous, the dominant burrower in Saginaw Bay. Assuming that solute fluxes from Saginaw Bay are representative of all of the post-glacial sediments of Lake Huron, the iodine flux from sediments is comparable to the total fluvial input of iodine. The extrapolated silica fluxes from Lake Huron sediments balance the estimated biogenic silica flux to the sediments.     

Phytoplankton and phosphorus in southern Georgian Bay, 1973–1982, and implications for phosphorus loading controls

The phytoplankton and nutrient status of the embayments between Penetanguishene and Waubaushene in southern Georgian Bay (Severn Sound) were examined during the ice-free periods of 1973–1982 because the area showed symptoms of excessive nutrient enrichment. Four wastewater treatment plants currently discharge to the area, another is under construction and a sixth plant has been proposed. Except for Penetang Bay, the area is well-mixed by prevailing winds but is somewhat isolated from the main part of Georgian Bay. Average phytoplankton biomasses throughout the area were 10–20× higher than values from adjacent Nottawasaga Bay where, during 1980, total phytoplankton biomass ranged between 0.15 and 0.25 mm³ · l^–1. Total phosphorus concentrations were highest in Penetang Bay, ranging between 30 and 49 µg P · l^–1 (May–September means) over the 10 year period. Phosphorus concentrations in Nottawasaga Bay averaged 4–6 µg P · l^–1 and no significant differences were detected among the sampling stations; however, phytoplankton densities at stations near urban centres and river inflows were significantly higher than at more remote offshore sites and attests to the use of phytoplankton as a sensitive measure of trophic status in Georgian Bay.Although improvement of Severn Sound water quality to a level comparable to that presently existing in Nottawasaga Bay may never be practical, steps are being taken to control high industrial phosphorus loading and to lessen bypassing of sewage treatment facilities previously hydraulically overloaded during periods of heavy runoff. These measures, along with an evaluation of other major sources of nutrients to Severn Sound, should enable a refinement of the nutrient management programme for Severn Sound and some improvement in trophic status.     

The determination of fresh organic carbon weight from formaldehyde preserved macrofaunal samples

Methodologies are presented whereby the fresh organic carbon weight of formaldehyde preserved macrofaunal samples may be estimated. Length-organic carbon weight regressions were determined for the four numerically dominant bivalves in Narragansett Bay, Rhode Island (Nucula annulata, Yoldia limatula, Mulinia lateralis, and Pandora gouldiana) and one commercially important, but less abundant species (Mercenaria mercenaria). Constants were determined to convert the dry weight of preserved softbodied organisms (polychaetes, oligochaetes, amphipods, etc.) to fresh (unpreserved) organic carbon weight. These results can be used by investigators studying the energetics of benthic communities similar to those in Narragansett Bay.     

Distribution and abundance of fishes in the San Francisco Bay estuary between 1980 and 1982

In 1980 a long-term study of the fishery resources of the San Francisco Bay estuary was initiated in an effort to delineate the importance of freshwater inflow to fish and invertebrate abundance and distribution in the bay. An analysis of the trawl data collected between January 1980 and December 1982 illustrates the influence of the timing and magnitude of freshwater inflows on fish fistribution and abundance in this estuary from the perspective of monthly, seasonal and annual time scales. Normally found in the delta, Suisun Bay and San Pablo Bay during periods of increased salinity, pelagic species moved downstream after the two peak flows studied, while demersal species usually found in Central San Francisco Bay moved upstream. Such upstream movements may be due in part to transport by strong density-driven currents.Timing and magnitude of monthly catches of some species varied on a seasonal cycle coincident with variations of freshwater inflow. Most species, especially the marine species, showed no consistent cycle of monthly catches. In the wet years of 1980 and 1982 the distributions of freshwater, estuarine and anadromous species were extended downstream into San Pablo, Central and South San Francisco Bays and some marine species, including the flatfish, were more abundant in the upstream areas. In the dry year of 1981 when bay salinities were higher, few marine species extended their distributions upstream into San Pablo and Suisun Bays. Jacksmelt was the only fish of the 15 most abundant species with its peak abundance in 1981. Most marine species were more abundant in the San Francisco Bay estuary in the wet years.