Infection of the brown alga Ectocarpus siliculosus by the oomycete Eurychasma dicksonii induces oxidative stress and halogen metabolism

Acknowledgments We would like to thank the Aberdeen Proteome Facility, especially Phil Cash, David Stead and Evelyn Argo for assistance with 2D electrophoresis and mass spectrometry. M.S. gratefully acknowledges a Marie Curie PhD fellowship from the European Commission (ECOSUMMER, MEST-CT-2005-20501), a joint FEMS/ESCMID Research Fellowship and the Genomia Fund. C.M.M.G. is supported by a Marie Curie postdoctoral fellowship (MEIF-CT-2006-022837), a Marie Curie Re-Integration Grant (PERG03-GA-2008-230865) and a New Investigator grant from the UK Natural Environment Research Council (NERC, grant NE/J00460X/1). F.C.K. would like to thank NERC for funding (grants NE/D521522/1, NE/F012705/1 and Oceans 2025 / WP 4.5). L.J.G.-B., C.M.M.G., F.C.K. and P.W. would like to acknowledge funding from NERC for a Strategic Ocean Funding Initiative award (NE/F012578/1). Funding from the MASTS pooling initiative (Marine Alliance for Science and Technology for Scotland, funded by the Scottish Funding Council and contributing institutions; grant reference HR09011) and from the TOTAL Foundation (Paris) to F.C.K. is gratefully acknowledged. Finally, we would like to thank the two anonymous referees for constructive suggestions to improve our manuscript.Peer reviewedPublisher PD

Transcriptomic profiling of the giant kelp, Macrocystis pyrifera, across environmental gradients

The giant kelp, Macrocystis pyrifera, spans gradients in light, temperature and nutrient availability both within its geographic distribution and the range of depths that individual sporophytes span. M. pyrifera is a member of the brown algae (Phaeophyceae), a complex multicellular group divergent from other eukaryotes; the application of sequence-based tools to study the ecology and evolution of this group is reviewed. To understand the biological response of this ecologically important alga to its environment, it is important to quantify the temporal scales of environmental variation. A several-year thermistor chain time series examined depth-specific variations in temperature and nutrients within a kelp bed. In addition to long-term seasonal changes, rapid vertical variations in the depth of the nutricline were observed, as much as 10m vertical displacement over the span of a few hours. Tools capable of examining the M. pyrifera physiological response on this temporal scale had not yet been developed. Due to the lack of available genomic data for the giant kelp, I utilized next-generation transcriptomic sequencing to increase the number of annotated transcriptional units for this species. M. pyrifera samples collected at different depths enabled transcriptomic exploration of metabolic function across environmental gradients. Depth-dependent transcription patterns were apparent and transcript annotation facilitated the identification of physiological responses to environmental factors. At the surface, where irradiance levels are highest and the potential for oxidative damage is most intense, physiological processes were focused on the capture of light energy for photosynthesis as well as protection from the damaging effects of the sun. M. pyrifera has multiple light harvesting complexes, including some in the LI818 group. Genes involved in nutrient acquisition, genetic information processing and degradation were more highly expressed at depth where colder temperatures and more nutrients occur. This dissertation provides the first transcriptomic characterization of M. pyrifera, develops sequenced-based tools and demonstrates their use to study transcriptional patterns in the context of this alga's natural and variable environmen

Observations of spawning in the Leather Bass, Dermatolepis dermatolepis (Teleostei: Epinephelidae), at Cocos Island, Costa Rica

Courtship and spawning behavior is described for the Leather Bass, Dermatolepis dermatolepis, from observations made from a manned submersible at Cocos Island, Costa Rica on 19 days between November 2006 and February 2007. Spawning occurred in the evening (16:00–18:30 h) in subgroups of 10–32 individuals that formed within aggregations of 50–70 individuals. The mating sequence was characterized by subgroup formation and crowding behavior followed by a brief vertical spawning rush, gamete release, and the rapid separation of participants. The aggregation was present on all dives, and spawning was not restricted to specific lunar phases

Observations of spawning in the Leather Bass, Dermatolepis dermatolepis (Teleostei: Epinephelidae), at Cocos Island, Costa Rica

Courtship and spawning behavior is described for the Leather Bass, Dermatolepis dermatolepis, from observations made from a manned submersible at Cocos Island, Costa Rica on 19 days between November 2006 and February 2007. Spawning occurred in the evening (16:00–18:30 h) in subgroups of 10–32 individuals that formed within aggregations of 50–70 individuals. The mating sequence was characterized by subgroup formation and crowding behavior followed by a brief vertical spawning rush, gamete release, and the rapid separation of participants. The aggregation was present on all dives, and spawning was not restricted to specific lunar phases

Baselines and degradation of coral reefs in the northern Line Islands

Effective conservation requires rigorous baselines of pristine conditions to assess the impacts of human activities and to evaluate the efficacy of management. Most coral reefs are moderately to severely degraded by local human activities such as fishing and pollution as well as global change, hence it is difficult to separate local from global effects. To this end, we surveyed coral reefs on uninhabited atolls in the northern Line Islands to provide a baseline of reef community structure, and on increasingly populated atolls to document changes associated with human activities. We found that top predators and reef-building organisms dominated unpopulated Kingman and Palmyra, while small planktivorous fishes and fleshy algae dominated the populated atolls of Tabuaeran and Kiritimati. Sharks and other top predators overwhelmed the fish assemblages on Kingman and Palmyra so that the biomass pyramid was inverted (top-heavy). In contrast, the biomass pyramid at Tabuaeran and Kiritimati exhibited the typical bottom-heavy pattern. Reefs without people exhibited less coral disease and greater coral recruitment relative to more inhabited reefs. Thus, protection from overfishing and pollution appears to increase the resilience of reef ecosystems to the effects of global warming

Short-term effects of co2, nutrients and temperature on three marine macroalgae under solar radiation

Three macroalgal species belonging to Chlorophyta (Ulva rigida), Rhodophyta (Ellisolandia elongata) and Phaeophyceae (Heterokontophyta; Cystoseira tamariscifolia), naturally growing at the same shore level and representing 3 morpho-functional groups, were exposed to short-term changes in temperature under different carbon and nitrogen regimes. Experiments were conducted in outdoor tanks at 4 combinations of carbon and nitrogen levels under reduced solar radiation. In vivo chl a fluorescence parameters and pigment contents were monitored to assess diurnal physiological responses and potential for recovery. Strong fluctuations in chl a fluorescence parameters, but not in chl a content, were observed in response to diurnal variation in solar radiation and light climate within the tanks; sensitivity varied between algal species and, in some cases, depended on the carbon and nitrogen regime. Nitrogen uptake was similarly high in U. rigida and E. elongata and lowest in C. tamariscifolia. In U. rigida and E. elongata, chl a concentrations decreased after high-carbon treatments. Effective photosystem II quantum efficiency was reduced in all species at noon, and lowest in C. tamariscifolia. The results highlight the complexity of physiological short-term acclimations which were most likely linked to biochemical changes at the cellular level. Long-term experiments are required in future for more comprehensive investigation of the observed interactive effects of the different environmental parameters