Martin Sayer

Occurrence and activity of mobile macrofauna on a sublittoral reef: Diel and seasonal variation

Underwater television observations were made of mobile macrofauna inhabiting two parts of a sublittoral reef on the west coast of Scotland for 48 h periods in spring, summer, autumn and winter. Continuous occurrence profiles (mean hourly frequency of occurrence, %) were detailed for 12 species of fish ( Chirolophis ascanii, Conger conger, Ctenolabrus rupestris, Lepadogaster candollei, Myoxocephalus scorpius, Pholis gunnellus, Pollachius pollachius, Raniceps raninus, Phrynorhombus regius, Zeugopterus punctatus, Thorogobius ephippiatus and Trisopterus minutus ), ten crustacean species ( Cancer pagurus, Carcinus maenas, Galathea strigosa, Homarus gammarus, Inachus spp., Munida rugosa, Necora puber , Brachyuran sp., Caridean sp. and Pagurid sp.) and four echinoderm species ( Antedon bifida, Asterias rubens, Hemicia oculata and Solaster endeca ). Rhythmic patterns of diel activity and/or occurrence were identified for several species. Chirolophis ascanii, Ctenolabrus rupestris, L. candollei, Myoxocephalus scorpius, Pholis gunnellus, Pollachius pollachius, Thorogobius ephippiatus, Trisopterus minutus and Munida rugosa were predominantly diurnal, but Ctenolabrus rupestris, Myoxocephalus scorpius and Trisopterus minutus also showed some evidence of crepuscular activity. Raniceps raninus activity was predominantly nocturnal but became continuous in summer. In other species (the topknots Phrynorhombus regius and Z. punctatus and the crustaceans Cancer pagurus and Homarus gammarus ) identifiable occurrence patterns changed with season or site. The greatest number of fish species occurred in winter with Myoxocephalus scorpius, Pollachius pollachius and topknots ( Phrynorhombus regius and Z. punctatus ) showing greater occurrence/activity during spring and winter. Co-occurrence analysis was used to identify species interactions or avoidances.

Factors affecting the performance of the acoustic ground discrimination system RoxAnn

Wilding, T. A., Sayer, M. D. J., and Provost, P. G. 2003. Factors affecting the performance of the acoustic ground discrimination system RoxAnn. e ICES Journal of Marine Science, 60: 1373e1380. The resolution, temporal variability and survey vessel speed dependence of the acoustic ground discrimination system RoxAnn was assessed over a 1 km 2 area in Loch Linnhe on the west coast of Scotland. The resolution of the system was relatively poor and of the sediment parameters quantified (stone cover and sediment texture), only stone cover was consistently and significantly related to the RoxAnn output. The output showed considerable variability over the same ground when sampled within the same day and between days and months. The effect of survey vessel speed on the output was also significant but highly variable during all surveys. The apparent magnitude and unpredictable nature of the variation in the RoxAnn output have implications for the use of such systems in habitat mapping, particularly when surveying biological communities where there are only small differences in the physical properties of the seabed and also where monitoring temporal change. These aspects are discussed.

SCUBA divers as oceanographic samplers: The potential of dive computers to augment aquatic temperature monitoring

Monitoring temperature of aquatic waters is of great importance, with modelled, satellite and in-situ data providing invaluable insights into long-term environmental change. However, there is often a lack of depth-resolved temperature measurements. Recreational dive computers routinely record temperature and depth, so could provide an alternate and highly novel source of oceanographic information to fill this data gap. In this study, a citizen science approach was used to obtain over 7,000 scuba diver temperature profiles. The accuracy, offset and lag of temperature records was assessed by comparing dive computers with scientific conductivity-temperature-depth instruments and existing surface temperature data. Our results show that, with processing, dive computers can provide a useful and novel tool with which to augment existing monitoring systems all over the globe, but especially in under-sampled or highly changeable coastal environments.

Evaluation of techniques used in the assessment of subtidal epibiotic assemblage structure

Abstract A comparative study was carried out to evaluate the efficiency of a number of techniques commonly used for assessing the structure of subtidal epifaunal communities. Assessments were made of the epifaunal assemblages fouling two substrata: concrete and PVC plastic. Where possible, each technique was undertaken in three ways, namely, in situ underwater, in the laboratory and using image analysis on photographs taken in situ. Comparisons were also made of biomass estimates made on samples taken in situ and in the laboratory. All method and technique combinations assessed detected differences in the epibiotic communities associated with the two fouling substrata. Sampling in situ, in the laboratory and using image analysis gave similar estimates of percent cover. However, there were significant differences in measurements made for most taxa with respect to abundance and frequency counts depending on how the technique was carried out. Laboratory-based sampling of abundance and frequency counts and biomass determinations, rather than in situ or image-analysis based sampling, are recommended for use in future studies of epifaunal fouling.

The potential of the marine bivalve mollusc Glossus humanus (L.) as a sclerochronological archive

In order to assess its potential as a sclerochronological archive, we present statistical and geochemical analyses of internal growth increment series in shells of the heart cockle Glossus humanus (L.), a large marine bivalve. The investigated samples were collected from Loch Sunart and the Sound of Mull, Scotland, United Kingdom. High-resolution stable isotope (δ18O) analyses and radiocarbon (14C) determinations indicated that G. humanus forms annual growth lines. Examination of the growth increment series revealed that the maximum longevity of G. humanus in this region was 78 years. Radiocarbon dating and crossmatching techniques, derived from dendrochronology, were used to provide an estimation of the temporal distribution of the fossil G. humanus. Of the shells that contained >25 growth increments, seven were found to statistically crossmatch, including shells from two distinct sites 15 km apart. The calibrated 14C determinations independently confirmed the crossmatching of three G. humanus shells from the Sound of Mull with a separately constructed Glycymeris glycymeris chronology and a further three G. humanus shells from site 3, in the main basin of Loch Sunart, but indicate a significant difference (site 1) in the antiquity of the two G. humanus populations. Radiocarbon dating indicated that, despite their fragile nature, G. humanus shells remain preserved in near original condition for at least 700 years. Given the small amount of available shell material, it is unlikely that G. humanus will become a key species for the construction of long absolutely dated sclerochronologies. However, these data do indicate that the annually resolved G. humanus growth series could be used to supplement series from other long-lived bivalves and facilitate the construction of a robust multispecies sclerochronology spanning the last 1000 years.

Reconstructing past seasonal to multi-centennial scale variability in the NE Atlantic Ocean using the long-lived marine bivalve mollusc Glycymeris glycymeris

The lack of long-term, highly resolved (annual to sub-annual) and absolutely dated baseline records of marine variability extending beyond the instrumental period (last ~50-100 years) hinders our ability to develop a comprehensive understanding of the role the ocean plays in the climate system. Specifically, without such records, it remains difficult to fully quantify the range of natural climate variability mediated by the ocean, and to robustly attribute recent changes to anthropogenic or natural drivers. Here we present a 211-year (1799-2010 CE; all dates hereafter are common era) seawater temperature (SWT) reconstruction from the northeast Atlantic Ocean derived from absolutely dated, annually resolved, oxygen isotope ratios recorded in the shell carbonate (δ18Oshell) of the long-lived marine bivalve mollusc Glycymeris glycymeris. The annual record was calibrated using sub-annually resolved δ18Oshell values drilled from multiple shells covering the instrumental period. Calibration verification statistics and spatial correlation analyses indicate that the δ18Oshell record contains significant skill at reconstructing Northeast Atlantic Ocean mean summer SWT variability associated with changes in sub-polar gyre (SPG) dynamics and the North Atlantic Current. Reconciling differences between the δ18Oshell data and corresponding growth increment width chronology demonstrates that 68% of the variability in G. glycymeris shell growth can be explained by the combined influence of biological productivity and SWT variability. These data suggest G. glycymeris can provide seasonal to multi-centennial absolutely dated baseline records of past marine variability that will lead to the development of a quantitative understanding of the role the marine environment plays in the global climate system.

Carbon assimilation and transfer through kelp forests in the NE Atlantic is diminished under a warmer ocean climate

Abstract Global climate change is affecting carbon cycling by driving changes in primary productivity and rates of carbon fixation, release and storage within Earths vegetated systems. There is, however, limited understanding of how carbon flow between donor and recipient habitats will respond to climatic changes. Macroalgal‐dominated habitats, such as kelp forests, are gaining recognition as important carbon donors within coastal carbon cycles, yet rates of carbon assimilation and transfer through these habitats are poorly resolved. Here, we investigated the likely impacts of ocean warming on coastal carbon cycling by quantifying rates of carbon assimilation and transfer in Laminaria hyperborea kelp forests—one of the most extensive coastal vegetated habitat types in the NE Atlantic—along a latitudinal temperature gradient. Kelp forests within warm climatic regimes assimilated, on average, more than three times less carbon and donated less than half the amount of particulate carbon compared to those from cold regimes. These patterns were not related to variability in other environmental parameters. Across their wider geographical distribution, plants exhibited reduced sizes toward their warm‐water equatorward range edge, further suggesting that carbon flow is reduced under warmer climates. Overall, we estimated that Laminaria hyperborea forests stored ~11.49 Tg C in living biomass and released particulate carbon at a rate of ~5.71 Tg C year−1. This estimated flow of carbon was markedly higher than reported values for most other marine and terrestrial vegetated habitat types in Europe. Together, our observations suggest that continued warming will diminish the amount of carbon that is assimilated and transported through temperate kelp forests in NE Atlantic, with potential consequences for the coastal carbon cycle. Our findings underline the need to consider climate‐driven changes in the capacity of ecosystems to fix and donate carbon when assessing the impacts of climate change on carbon cycling.

Arctic marine phytobenthos of northern Baffin Island

Global climate change is expected to alter the polar bioregions faster than any other marine environment. This study assesses the biodiversity of seaweeds and associated eukaryotic pathogens of an established study site in northern Baffin Island (72° N), providing a baseline inventory for future work assessing impacts of the currently ongoing changes in the Arctic marine environment. A total of 33 Phaeophyceae, 24 Rhodophyceae, 2 Chlorophyceae, 12 Ulvophyceae, 1 Trebouxiophyceae, and 1 Dinophyceae are reported, based on collections of an expedition to the area in 2009, complemented by unpublished records of Robert T. Wilce and the first‐ever photographic documentation of the phytobenthos of the American Arctic. Molecular barcoding of isolates raised from incubated substratum samples revealed the presence of 20 species of brown seaweeds, including gametophytes of kelp and of a previously unsequenced Desmarestia closely related to D. viridis, two species of Pylaiella, the kelp endophyte Laminariocolax aecidioides and 11 previously unsequenced species of the Ectocarpales, highlighting the necessity to include molecular techniques for fully unraveling cryptic algal diversity. This study also includes the first records of Eurychasma dicksonii, a eukaryotic pathogen affecting seaweeds, from the American Arctic. Overall, this study provides both the most accurate inventory of seaweed diversity of the northern Baffin Island region to date and can be used as an important basis to understand diversity changes with climate change.

Use of decompression computers as dive profilers and electronic logbooks, and in the management of decompression sickness treatment

Many decompression computers developed for the SCUBA leisure market over the past five years have the facility to store profile information which can be interrogated through PC interfaces. This capability allows for a variety of dive parameters to be stored, and subsequently downloaded [I]. The Natural Environment Research Council (NERC) Cent re for Oiving at Ounstaffnage, has been using a number of models of decompression computers over the past two years. Their use has been as dive loggers, and examples of the parameter categories recorded, and at what level of precision, are presented here in brief. The NERC Centre also accommodates a hyperbaric treatment facility. The availability of the software and PC interfaces necessary to download from most models of dive computers, has allowed for the incorporation of actual recorded dive details within the treatment management process. The benefits of having that additional information, usually at the commencement of the treatment, are discussed below. lt is not intended here to give a detailed product guide of downloadable computers, and a systematic investigation of all types of computers has not been attempted. The purpose of this note is to summarise the uses of such computers to the diving at work and hyperbaric treatment communities. Use of decompression computers as dive profilers and electronic logbooks