ALBERT

Description: Quorum sensing (QS) signals have been considered to play important roles in biofilm development and in the attractiveness of biofilms to higher organisms in marine ecosystem. In this study, bacterial QS signalsacylated homoserine lactone derivatives (AHLs) were detected in 2-, 4-, and 6-day-old subtidal biofilms by using AHLs reporter strains. N-dodecanoyl-homoserine lactone (C12-HSL) was identified in 6-day-old biofilm at a concentration of 9.04 μg cm−minus;2 (3.36 mmol l−minus;1). To investigate the possible role of AHLs in the consequent eventlarval settlement of the polychaete Hydroides elegans onto subtidal biofilmsseven biofilm-derived bacteria that effectively induced larval settlement of H. elegans, were screened for AHL production. One of them, the Vibrio sp. UST950701-007, produced N-hexanoyl-homoserine lactone (C6-HSL). Larval settlement bioassay showed that C6-HSL, C12-HSL, and 3-oxo-octanoyl-homoserine lactone (3-oxo-C8-HLS) at certain concentrations induced some initial larval settlement behaviors such as reducing swimming speed, crawling on the bottom. However, these AHLs did not effectively induce larval settlement in comparison to the effective settlement inducer 3-isobutyl-1-methylxanthine. The possible chemokinetic mechanism and indirect effects of AHLs on larval settlement are suggested.

Description:  An ensemble of twenty four coupled ocean-atmosphere models has been compared with respect to their performance in the tropical Pacific. The coupled models span a large portion of the parameter space and differ in many respects. The intercomparison includes TOGA (Tropical Ocean Global Atmosphere)-type models consisting of high-resolution tropical ocean models and coarse-resolution global atmosphere models, coarse-resolution global coupled models, and a few global coupled models with high resolution in the equatorial region in their ocean components. The performance of the annual mean state, the seasonal cycle and the interannual variability are investigated. The primary quantity analysed is sea surface temperature (SST). Additionally, the evolution of interannual heat content variations in the tropical Pacific and the relationship between the interannual SST variations in the equatorial Pacific to fluctuations in the strength of the Indian summer monsoon are investigated. The results can be summarised as follows: almost all models (even those employing flux corrections) still have problems in simulating the SST climatology, although some improvements are found relative to earlier intercomparison studies. Only a few of the coupled models simulate the El Niño/Southern Oscillation (ENSO) in terms of gross equatorial SST anomalies realistically. In particular, many models overestimate the variability in the western equatorial Pacific and underestimate the SST variability in the east. The evolution of interannual heat content variations is similar to that observed in almost all models. Finally, the majority of the models show a strong connection between ENSO and the strength of the Indian summer monsoon.

Description: We describe the behaviour of 23 dynamical ocean-atmosphere models, in the context of comparison with observations in a common framework. Fields of tropical sea surface temperature (SST), surface wind stress and upper ocean vertically averaged temperature (VAT) are assessed with regard to annual mean, seasonal cycle, and interannual variability characteristics. Of the participating models, 21 are coupled GCMs, of which 13 use no form of flux adjustment in the tropics. The models vary widely in design, components and purpose: nevertheless several common features are apparent. In most models without flux adjustment, the annual mean equatorial SST in the central Pacific is too cool and the Atlantic zonal SST gradient has the wrong sign. Annual mean wind stress is often too weak in the central Pacific and in the Atlantic, but too strong in the west Pacific. Few models have an upper ocean VAT seasonal cycle like that observed in the equatorial Pacific. Interannual variability is commonly too weak in the models: in particular, wind stress variability is low in the equatorial Pacific. Most models have difficulty in reproducing the observed Pacific 'horseshoe' pattern of negative SST correlations with interannual Niño3 SST anomalies, or the observed Indian-Pacific lag correlations. The results for the fields examined indicate that several substantial model improvements are needed, particularly with regard to surface wind stress.

Description: Cephalopods are highly sensitive to environmental conditions and changes at a range of spatial and temporal scales. Relationships documented between cephalopod stock dynamics and environmental conditions are of two main types: those concerning the geographic distribution of abundance, for which the mechanism is often unknown, and those relating to biological processes such as egg survival, growth, recruitment and migration, where mechanisms are sometimes known and in a very few cases demonstrated by experimental evidence. Cephalopods seem to respond to environmental variation both ‘actively’ (e.g. migrating to areas with more favoured environmental conditions for feeding or spawning) and ‘passively’ (growth and survival vary according to conditions experienced, passive migration with prevailing currents). Environmental effects on early life stages can affect life history characteristics (growth and maturation rates) as well as distribution and abundance. Both large-scale atmospheric and oceanic processes and local environmental variation appear to play important roles in species–environment interactions. While oceanographic conditions are of particular significance for mobile pelagic species such as the ommastrephid squids, the less widely ranging demersal and benthic species may be more dependent on other physical habitat characteristics (e.g. substrate and bathymetry). Coastal species may be impacted by variations in water quality and salinity (related to rainfall and river flow). Gaps in current knowledge and future research priorities are discussed. Key research goals include linking distribution and abundance to environmental effects on biological processes, and using such knowledge to provide environmental indicators and to underpin fishery management.

Description: The aim of this study was to determine whether the experimental nutrient enrichment of littoral rocky shore communities would be followed by a predicted accumulation of fast-growing opportunistic algae and a subsequent loss of perennial benthic vegetation. Inorganic nitrogen (N) and potassium (P) was added to eight concrete mesocosms inhabited by established littoral communities dominated by fucoids. The response to nutrient enrichment was followed for almost 2 1/2 years. Fast-growing opportunistic algae (periphyton and ephemeral green algae) grew significantly faster in response to nutrient enrichment, but the growth of red filamentous algae and large perennial brown algae was unaffected. However, these changes were not followed by comparable changes in the biomass and composition of the macroalgae. The biomass of opportunistic algae was stimulated only marginally by the nutrient enrichment, and perennial brown algae (fucoids) remained dominant in the mesocosm regardless of nutrient treatment level. Established rocky shore communities thus seem able to resist the effects of heavy nutrient loading. We found that the combined effects of the heavy competition for space and light imposed by canopy-forming algae, preferential grazing on opportunistic algae by herbivores, and physical disturbance, succeeded by a marked export of detached opportunistic algae, prevented the fast-growing algae from becoming dominant. However, recruitment studies showed that the opportunistic algae would become dominant when free space was available under conditions of high nutrient loading and low grazing pressure. These results show that established communities of perennial algae and associated fauna in rocky shore environments can prevent or delay the accumulation of bloom-forming opportunistic algae and that the replacement of long-lived macroalgae by opportunistic species at high nutrient loading may be a slow process. Nutrient enrichment may not, in itself, be enough to stimulate structural changes in rocky shore communities.

Description: Dissolved and particulate metals (Ag, Cd, Co, Cu, Ni, and Zn) and nutrients (PO4, NO3, and H4SiO4) were measured in Todos Santos Bay (TSB) in August 2005. Two sources producing local gradients were identified: one from a dredge discharge area (DDA) and another south of the port and a creek. The average concentrations of dissolved Cd and Zn (1.3 and 15.6 nM, respectively) were higher by one order of magnitude than the surrounding Pacific waters, even during upwelling, and it is attributed to the presence of a widespread and long-lasting red tide coupled with some degree of local pollution. A clear spatial gradient (10 to 6 pM), from coast to offshore, of dissolved Ag was evident, indicating the influence of anthropogenic inputs. The particulate fraction of all metals, except Cu, showed a factor of ~3 decrease in concentrations from the DDA to the interior of the bay. The metal distributions were related to the bay’s circulation by means of a numerical model that shows a basically surface-wind-driven offshore current with subsurface compensation currents toward the coast. Additionally, the model shows strong vertical currents over the DDA. Principal component analysis revealed three possible processes that could be influencing the metal concentrations within TSB: anthropogenic inputs (Cd, Ag, and Co), biological proceses (NO3, Zn, and Cu), and upwelling and mixing (PO4, H4SiO4, Cd, and Ni). The most striking finding of this study was the extremely high Cd concentrations, which have been only reported in highly contaminated areas. As there was a strong red tide, it is hypothesized that the dinoflagellates are assimilating the Cd, which is rapidly remineralized and being concentrated on the stratified surface layers.

Description: Analysis of ten- and four-year datasets for the large, shallow, subtropical, and eutrophic Lakes Okeechobee (USA) and Taihu (China), respectively, suggest that resource-ratio explanations for cyanobacteria dominance may not apply to these two lakes. Datasets were examined to identify relationships between nutrient ratios [total nitrogen (TN):total phosphorus (TP) and ammonium (NH4+):oxidized N (NOx)] and phytoplankton community structure (as proportions of cyanobacteria and diatoms to total phytoplankton biomass). Datasets were pooled by sampling month, averaged lake-wide, and analyzed with linear regression. In Okeechobee, the cyanobacteria proportion increased and the diatom proportion decreased with increasing TN:TP. In Taihu, cyanobacteria decreased with increasing TN:TP, but the opposite trend observed for diatoms was marginally significant. Okeechobee cyanobacteria increased and diatoms decreased with increasing NH4+:NOx, but no significant relationships between phytoplankton and NH4+:NOx were observed in Taihu. Both lakes had significant relationships between phytoplankton community structure and total nutrients, but these relationships were the opposite of those expected. Relationships between phytoplankton community structure and water quality parameters from the previous month resulted in improved relationships, suggesting a predictive capability. Statistical analysis of the entire datasets (not pooled) supported these and additional relationships with other parameters, including temperature and water clarity.

Description: Based on the re-interpretation of published data, the von Bertalanffy growth function parameters of the coelacanth, Latimeria chalumnae, are estimated as L∞=218 cm total length, s.e. 23; K=0.059 (year−1), s.e. 0.012; t0=−3.3 (year), s.e. 0.5, corresponding to a life span of 48 years. The length–weight relationship of the form W=a*TL∧b, with wet weight (W) in g and total length (TL) in cm, is estimated as a=0.0278, b=2.89, r2=0.893, n=87, range=42.5–183 cm TL. Using extreme value theory, the maximum length for female coelacanths is estimated as 199 cm TL (95% confidence interval=175–223 cm TL) and for males as 168 cm TL (95% confidence interval 155–180 cm TL). Based on data from seven females with embryos or mature eggs, the length-at-first-maturity for females is estimated to be about 150 cm TL, corresponding to an age of about 16 years. Based on the value of t0=−3.3 years and on the presence of three scale rings found in a newborn coelacanth, the period of embryogenesis lasts for about three years, the longest known in vertebrates. The natural mortality rate is estimated at M=0.12. Population food consumption is found to be 1.4 times the existing biomass per year, and gross food conversion efficiency indicates that only 10% of the consumed food is utilized for somatic growth.