A new generation of coastal monitoring platforms

The need for new instruments and systems for environment monitoring encouraged the development of a network of coastal platforms combining a high versatility with ease of use and affordability. Almost every instrument can be fitted on the platforms, thanks to the large amount of available power provided by both solar panels and wind generators. All the platforms host a pumping system that pumps water from five depths into a measurement chamber where a multiparametric probe is fitted and from where other devices (e.g. samplers or analysers) can draw samples. In situ temperature measurements are provided at the same pumping depths. A colorimetric nutrient analyser and a meteorological station complete the basic equipment. On one of the platforms, a remotely controlled water sampler and an ADCP are also fitted. The data-acquisition and transmission system enables the platform to be controlled remotely using a special macro-commands set. Several examples of use are presented.     

Control of larval release in the Caribbean spiny lobster, <Emphasis Type="Italic">Panulirus argus</Emphasis>: role of chemical cues

The current model for larval release in subtidal crustaceans suggests that hatching time is controlled by the embryos, which release a pheromone that stimulates the parent female to undergo behaviors that synchronize larval release. Alternatively, hatching could be controlled by the females. Ovigerous spiny lobsters Panulirus argus (Latreille) exhibit stereotypic behaviors during larval release, including rapid abdominal extensions and pleopod-pumping activity. Ovigerous P. argus were collected from coral reefs in the Florida Keys, USA during the summers of 2005 and 2006. Pleopod-pumping activity was quantified to determine if a female’s pumping activity correlates with the developmental state of the embryos. The role of pheromones released by developing and hatching embryos in controlling pumping behaviors was tested by measuring the pumping response of ovigerous lobsters to (1) hatch water, (2) homogenized embryo water, (3) embryo-conditioned water (unhatched late-stage embryos soaked for 20 h), and (4) water containing homogenized post-hatch embryo cases. Bioassays were conducted under constant conditions (dim-red light) in the laboratory at random times during the day to control for any possible rhythm in pumping activity. Spontaneous pleopod-pumping activity increased significantly with increasing embryo development. Upon exposure to hatch water, ovigerous lobsters with late-stage embryos displayed increased pleopod pumping with increased treatment concentration. Water individually conditioned with homogenized late-stage embryos, intact late-stage embryos, and homogenized post-hatch embryo cases all induced larval release behaviors in females with late-stage embryos. Ovigerous females with early-stage embryos did not respond to water conditioned with homogenized early- or late-stage embryos. These results suggest that active substances are released by embryos at the time of hatching and induce the stereotypical pumping behaviors of the female that synchronizes larval release. The results support the model that larval release in subtidal crustaceans is controlled by pheromones released from hatching embryos.     

Enhanced oil recovery water requirements

Water requirements for enhanced oil recovery (EOR) are thoroughly evaluated using publicly available information, data from actual field applications and information provided by knowledgeable EOR technologists in fourteen major oil companies. Water quanity and quality requirements are estimated for individual EOR processes (steam drive,in situ combustion and carbon dioxide, micellar-polymer, polymer and caustic flooding) in those states and specific geographical locations where these processes will likely play major roles in future petroleum production by the year 2000. The estimated quantity requirements represent thetotal water needed from all sources, e.g. aquifers, lakes and produced water. A reduction in these quantities can be achieved by reinjecting all of the produced water potentially available for recyle, e.g. some is lost in oil and water separation and water treatment processes, in the oil recovery method. For injection water quality requirements, it is noted that not all of the water used for EOR needs to be fresh. The use oftreated produced water can significantly reduce the quantities of fresh water that would be sought from other sources. Although no major EOR project to date has been abandoned because of water supply problems, competing regional uses for water, drought situations, and scarcity of high quality, e.g. low total dissolved solids, surface water and ground water could be impediments to certain projects in the near future.     

Growth of the rock lobster Jasus lalandii and its relationship to benthos

Growth increments of the male rock lobster Jasus lalandii vary systematically with location within a small (38 km²) fishing ground off the South African west coast. High growth rates were recorded from an area where the availability of benthos suitable as rock-lobster food was also high. Increments could also be shown to vary significantly in different years, but over the size range examined, growth did not appear to be a function of size. Benthic biomass was found to be inversely related to depth. However, comparisons between biomass values from the same depths in two different areas of the fishing ground suggested that biomass was higher in areas which were in proximity to shallow water, where extensive kelp beds were found. Mussels (Aulacomya magellanica) formed an important constituent of the rock lobster's diet; these were prevalent at depths between 20 and 40 m, and especially in areas where rock-lobster growth rates were high.     

Biology of the basket star <Emphasis Type="Italic">Gorgonocephalus caputmedusae</Emphasis> (L.)

Ophiurid basket stars belonging to the family Gorgonocephalidae are distributed from the Arctic to the Antarctic and from the shallow subtidal to the deep sea, but their biology remains poorly known. In situ observations at the mouth of the Oslofjord by a remotely operated vehicle showed that Gorgonocephalus caputmedusae had a patchy distribution at 85 to 120 m water depth and frequently occurred in association with the gorgonian Paramuricea placomus and the coral Lophelia pertusa. Morphological and histological studies show that G. caputmedusae is well adapted to capture macroplanktonic prey. Histological examination of the arms revealed the presence of a thick layer of dermal mutable connective tissue which is probably an energy-efficient way to maintain its feeding posture against the current. This layer is connected to the nerve cord suggesting that the passive mechanical properties (stiffness) is controlled by the nervous system. In the distal parts of the arms, each segment has a pair of sticky tube feet and a sophisticated system of spines and hooks, which are connected to muscles and collagenous tendons. In combination, these features were shown, in an experimental flume study, to be used for capturing the locally abundant krill species Meganyctiphanes norvegica. This is the first documentation of G. caputmedusae of this kind.     

Feeding behavior of the ctenophore <Emphasis Type="Italic">Thalassocalyce inconstans</Emphasis>: revision of anatomy of the order Thalassocalycida

Behavioral observations using a remotely operated vehicle (ROV) in the Gulf of California in March, 2003, provided insights into the vertical distribution, feeding and anatomy of the rare and delicate ctenophore Thalassocalyce inconstans. Additional archived ROV video records from the Monterey Bay Aquarium Research Institute of 288 sightings of T. inconstans and 2,437 individual observations of euphausiids in the Gulf of California and Monterey Canyon between 1989 and 2005 were examined to determine ctenophore and euphausiid prey depth distributions with respect to temperature and dissolved oxygen concentration [dO]. In the Gulf of California most ctenophores (96.9%) were above 350 m, the top of the oxygen minimum layer. In Monterey Canyon the ctenophores were more widely distributed throughout the water column, including the hypoxic zone, to depths as great as 3,500 m. Computer-aided behavioral analysis of two video records of the capture of euphausiids by T. inconstans showed that the ctenophore contracted its bell almost instantly (0.5 s), transforming its flattened, hemispherical resting shape into a closed bi-lobed globe in which seawater and prey were engulfed. Euphausiids entrapped within the globe displayed a previously undescribed escape response for krill (‘probing behavior’), in which they hovered and gently probed the inner surfaces of the globe with antennae without stimulating further contraction by the ctenophore. Such rapid bell contraction could be effected only by a peripheral sphincter muscle even though the presence of circumferential ring musculature was unknown for the Phylum Ctenophora. Thereafter, several live T. inconstans were collected by hand off Barbados and microscopic observations confirmed that assumption.     

Does the composition of the demersal fish assemblages in temperate coastal waters change with depth and undergo consistent seasonal changes?

The aim of this study was to determine whether the composition of the demersal fish fauna in coastal marine waters in temperate Australia changes markedly with increasing water depth and distance from the shore and whether the composition of the fish fauna in water depths of 5 to 35 m undergoes cyclic, seasonal changes. Samples of demersal fishes were therefore collected by trawling over the predominantly sandy substrate at nine sites located in water depths of 5 to 15 m or 20 to 35 m and within 20 km of the shore in four regions along ∼200 km on the lower west coast of Australia. The sampling regime involved trawling for fishes at each site at night in seven consecutive seasons between the summer of 1990/1991 and winter of 1992. A total of 72 435 fishes, representing 77 families, 143 genera and 172 species was caught. The compositions of the fish faunas in offshore waters with depths of 5 to 35 m were shown to differ markedly from those previously recorded for nearshore marine waters in the same regions. However, as some species, such as Sillago burrus, S. vittata, S. bassensis and Rhabdosargus sarba, increase in size, they move out from their nursery areas in nearshore waters into deeper and more offshore waters, where spawning occurs. Ordination showed that, in each of the four regions, the composition of the fish fauna in depths of 5 to 15 m differs from that in depths of 20 to 35 m. This difference is attributable to the fact that some species, such as  S. burrus, S. vittata and Upeneichthys lineatus, are far more abundant in depths of 5 to 15 m, whereas other species, such as S. robusta, U. stotti and Lepidotrigla modesta, occur predominantly in depths of 20 to 35 m. However, the samples collected from the single site that was inshore but in deeper water demonstrate that the composition of the fish fauna is influenced by distance from shore as well as by water depth. The compositions of the fish faunas differed with latitude, largely due to the fact that some subtropical species, such as Polyspina piosae, S. burrus and  S. robusta, did not extend down into the more southern regions. Ordination also showed that the composition of the fish faunas at all but one of the nine sites underwent pronounced and consistent cyclic, seasonal changes. This seasonal cyclicity at the different sites was attributable to sequential patterns of immigrations and emigrations by a number of fish species during the course of the year. These seasonal migrations involved, inter alia (1) movements of certain species from their nursery areas into these deeper waters, e.g.  S. bassensis and Scobinichthys granulatus; (2) migrations into and off the sandy areas of the inner continental shelf, e.g. Arnoglossus muelleri; (3) migrations to spawning areas, e.g. Sillago robusta; and (4) movements into areas where detached macrophytes accumulate in winter, e.g. Cnidoglanis macrocephalus and Apogon rueppellii. Received: 21 August 1998 / Accepted: 9 February 1999     

Water-level based discrete integrated dynamic control to regulate the flow for sewer-WWTP operation

• A model-free sewer-WWTP integrated control was proposed. • A dynamic discrete control based on the water level was developed. • The approach could improve the sewer operation against flow fluctuation. • The approach could increase transport capacity and enhance pump efficiency. This study aims to propose a multi-point integrated real-time control method based on discrete dynamic water level variations, which can be realized only based on the programmable logic controller (PLC) system without using a complex mathematical model. A discretized water level control model was developed to conduct the real-time control based on data-automation. It combines the upstream pumping stations and the downstream influent pumping systems of wastewater treatment plant (WWTP). The discretized water level control method can regulate dynamic wastewater pumping flow of pumps following the dynamic water level variation in the sewer system. This control method has been successfully applied in practical integrated operations of sewer-WWTP following the sensitive flow disturbances of the sewer system. The operational results showed that the control method could provide a more stabilized regulate pumping flow for treatment process; it can also reduce the occurrence risk of combined sewer overflow (CSO) during heavy rainfall events by increasing transport capacity of pumping station and influent flow in WWTP, which takes full advantage of storage space in the sewer system.     

Oxygen dynamics and transport in the Mediterranean sponge Aplysina aerophoba

The Mediterranean sponge Aplysina aerophoba kept in aquaria or cultivation tanks can stop pumping for several hours or even days. To investigate changes in the chemical microenvironments, we measured oxygen profiles over the surface and into the tissue of pumping and non-pumping A. aerophoba specimens with Clark-type oxygen microelectrodes (tip diameters 18–30 μm). Total oxygen consumption rates of whole sponges were measured in closed chambers. These rates were used to back-calculate the oxygen distribution in a finite-element model. Combining direct measurements with calculations of diffusive flux and modeling revealed that the tissue of non-pumping sponges turns anoxic within 15 min, with the exception of a 1 mm surface layer where oxygen intrudes due to molecular diffusion over the sponge surface. Molecular diffusion is the only transport mechanism for oxygen into non-pumping sponges, which allows total oxygen consumption rates of 6–12 μmol cm⁻³ sponge day⁻¹. Sponges of different sizes had similar diffusional uptake rates, which is explained by their similar surface/volume ratios. In pumping sponges, oxygen consumption rates were between 22 and 37 μmol cm⁻³ sponge day⁻¹, and the entire tissue was oxygenated. Combining different approaches of direct oxygen measurement in living sponges with a dynamic model, we can show that tissue anoxia is a direct function of the pumping behavior. The sponge-microbe system of A. aerophoba thus has the possibility to switch actively between aerobic and anaerobic metabolism by stopping the water flow for more than 15 min. These periods of anoxia will greatly influence physiological variety and activity of the sponge microbes. Detailed knowledge about the varying chemical microenvironments in sponges will help to develop protocols to cultivate sponge-associated microbial lineages and improve our understanding of the sponge-microbe-system.     

The regulation of a spatially heterogeneous externality: Tradable groundwater permits to protect streams

Groundwater pumping can reduce the flow of surface water in nearby streams. In the United States, recent awareness of this externality has led to intra- and inter-state conflict and rapidly-changing water management policies and institutions. Although the marginal damage of groundwater use on stream flows depends crucially on the location of pumping relative to streams, current regulations are generally uniform over space. We use a population data set of irrigation wells in the Nebraska portion of the Republican River Basin to analyze whether adopting spatially differentiated groundwater pumping regulations leads to significant reductions in farmer abatement costs and costs from damage to streams. We find that regulators can generate most of the potential savings in total social costs without accounting for spatial heterogeneity. However, if regulators need to increase the protection of streams significantly from current levels, spatially differentiated policies will yield sizable cost savings.     

Anthropogenic disturbance of deep-sea megabenthic assemblages: a study with remotely operated vehicles in the Faroe-Shetland Channel,NE Atlantic

The effects of local-scale anthropogenic disturbance from active drilling platforms on epibenthic megafaunal abundance, diversity and assemblage pattern were examined in two west of Shetland hydrocarbon fields at 420 and 508 m water depth. These areas were selected to include a range of disturbance regimes and contrasting faunal assemblages associated with different temperature regimes. Remotely operated vehicle (ROV) video provided high-resolution megafaunal abundance and diversity data, which were related to the extent of visible disturbance from drilling spoil. These data, in conjunction with a study deeper in the Faroe-Shetland Channel, have allowed comparison of the effects of disturbance on megabenthos across a range of sites. Disturbance to megafaunal assemblages was found to be high within 50 m of the source of drill spoil and in areas where spoil was clearly visible on the seabed, with depressed abundances (Foinaven 1,900 individuals ha⁻¹; Schiehallion 2,178 individuals ha⁻¹) and diversity (H′ = 1.75 Foinaven; 1.12 Schiehallion) as a result of smothering effects. These effects extended to around 100 m from the source of disturbance, although this was variable, particularly with current regime and nature of drilling activity. Further from the source of disturbance, megafaunal assemblages became more typical of the background area with increased diversity (H′ = 2.02 Foinaven; 1.77 Schiehallion) and abundance (Foinaven 16,484 individuals ha⁻¹; Schiehallion 5,477 individuals ha⁻¹). Visible effects on megafaunal assemblages as a result of seabed drilling were limited in extent although assemblage responses were complex, being controlled by differing effects to individual species often based on their motility.     

Ein fotoschlitten für biologische und geologische kartierungen des meeresbodens

A photosledge is described; it is 4 m long and 2 m wide and can be used also on an uneven sea bottom. In its foremost part a camera is mounted in a pressure sphere which has been tested for water depths down to 6,000 m. The camera system can hold 90 m of film; with an exposure size of 24x24 mm this accounts for 3,600 exposures. The time between 2 exposures may be varied from 1 to 10 sec and this allows to cover a distance of 2 to 20 nautical miles at a speed of 2 knots within 1 single mission. The photographic angle may be changed from vertical to horizontal. Best results have been obtained with angles of 30 and 45 degrees from the vertical. The electronic flash, with a power of 60 Wsec, is mounted below the camera. Successful work has been conducted in the North Sea and the Baltic Sea at depths between 40 and 50 m, on the continental slope off Portugal between depths of 140 and 240m, and on top of Great Meteor Seamount at depths between 280 and 350 m.     

House formation and feeding behaviour of<Emphasis Type="Italic"> Fritillaria borealis</Emphasis> (Appendicularia: Tunicata)

Numerous marine animals use elaborate filtration mechanisms to feed on particles suspended in the sea. Video-microscopy reveals that the common appendicularian Fritillaria borealis do so in a unique way. They live inside acellular, mucous houses, where their tail undulations act like a peristaltic pump in a close-fitting tail chamber to force water through a complex set of filters. Suspended particles, between ~0.2 and 30 µm in diameter, are retained in this process and propagated towards the mouth of the organism to be ingested. Coarser particles are back-washed out of the house during brief intervals of tail arrest, when the elastic recoil of the house walls reduces its volume to one-eighth of its inflated state. At the same time, the bifurcated tip of the animal's tail slides into a sleeve-like extension of the house. This sleeve acts like a flipper to propel the animal and collapsed house several millimetres to a few centimetres through the sea as soon as muscular activity of the tail is resumed. After a second tail arrest, a special muscular twist brings the tail out of the sleeve, whereupon undulatory pumping movements are resumed to reinflate and process particle-laden water through the house. The complete behavioural cycle lasts ~30 s. The repetitive inflation and deflation cycles of the house are probably of importance for unclogging of the coarse "inlet" filters downstream to the tail pump, as well as for agglutination of the smallest food particles trapped in the house to ease their recapture in the endostylar pharyngeal filter during the ingestion process. The unique tail sleeve and flipper at the same time enable the animal to move away from the previously filtered water and rejected coarse particles, before the house is reinflated for resumed food filtration.     

Loss of genetic diversity in Harpacticoida near offshore platforms

Offshore oil and gas production platforms can be a source of chronic stress that could lead to sublethal impacts on resident benthic organisms. In June 1993 and January 1994, genetic diversity of Harpacticoida (Copepoda) living proximal to operating, offshore platforms in the Gulf of Mexico was estimated to test if platforms are associated with strong selective pressures. Because harpacticoids have short generation times and direct benthic development, they are suitable organisms for examining population responses. Genetic diversity was estimated by comparing restriction fragment length polymorphisms generated from mitochondrial DNA amplified by the polymerase chain reaction on individuals of five species (Cletodes sp., Enhydrosoma pericoense, Normanella sp., Robertsonia sp., and Tachidiella sp.). Populations living at Near regions (stations<50 m from a platform) had significantly less haplotype diversity than populations of the same species living at Far regions (stations>3 km from a platform). The levels of haplotype diversity exhibited by the Far populations were similar at three different platforms located hundreds of kilometers apart. The differences in haplotype diversity between Near and Far regions were the result of a higher proportion of dominant haplotypes, and a loss of less common haplotypes. Haplotypic diversity was inversely correlated with a multivariate measurement of levels of sediment contaminants. The pattern of haplotype diversity on the Gulf of Mexico continental shelf seems to consist of a uniform level of haplotype diversity, punctuated by islands of lower diversity around oil and gas platforms. The selective pressures that lead to a loss of genetic diversity may be the result of contaminants, other differences in the physico-chemical environment, or disturbance in general.     

Movement and environmental preferences of Greenland sharks (<Emphasis Type="Italic">Somniosus microcephalus</Emphasis>) electronically tagged in the St. Lawrence Estuary,Canada

Three Greenland sharks (Somniosus microcephalus) were tagged with electronic tags, in Baie St. Pancrace, St. Lawrence Estuary, Quebec, Canada. One shark was tagged on 23 July 2004, with an acoustic telemetry tag. Two sharks were each tagged with a pop-up satellite archival tag (PSAT) on 27 August 2004. Two of the sharks remained in or close to the bay, one for 47 days and the other for at least 66 days. The third shark left the bay immediately after tagging on 27 August 2004. This shark entered the main channel of the St. Lawrence Estuary, and had moved 114.9 km upstream by 1 November 2004 when the tag reported to ARGOS satellites. The tags provided a total of 179 days of data on the movement and environmental preferences of Greenland sharks in the St. Lawrence Estuary. Sharks that reported depth and ambient water temperature data from the bay showed significant diel differences in depth preferences and corresponding ambient temperatures. The sharks remained near the bottom of the water column during the day and displayed increased vertical movements at night. The shark that resided in the main channel did not show this pattern, but generally remained at depths between 325 and 352 m. Sharks in the bay experienced water temperatures that ranged from −1.1 to 8.6°C at depths from 0 to 67 m. In the main channel the shark experienced temperatures that ranged from 1.0 to 5.4°C at depths from 132 to 352 m. This is the first report of numerous Greenland sharks inhabiting shallow near shore bays during summer and autumn.     

Phosphorus release potential and pollution characteristics of sediment in downstream Nansi Lake, China

The research aimed to evaluate present and potential phosphorous pollution due to high sedimentary phosphorus load and release from sediment, when external phosphorus was reduced in downstream Nansi Lake. Pollution load of the sediment and overlying water was investigated. Kinetics and isotherms of adsorption/release of sedimentary phosphorus were studied to determine equilibrium phosphate concentration (EPC₀) and release potential. Kinetics of phosphorus adsorption on sediment and release from sediment were well described by both the pseudo-first-order rate equation and the pseudo-second-order rate equation, but more appropriate to the pseudo-second-order rate equation with the adsorption/release capacity more close to the measured values, suggesting that the processes were chemically rate controlled and dependent on adsorption capacity. Soluble reactive phosphorus (SRP) sorption isotherms on sediment were best fitted by the modified Langmuir model indicating a monolayer adsorption. By comparing EPC₀ and SRP of water, the status (adsorption, releasing or in equilibrium) of sediment phosphorus could be determined. The sediments at site S1, S3, S4, S5, and S7 where the EPC₀s were greater than the SRPs, had a potential to release phosphorus into the water column. However, those sediments at S9, S10, and S12, where the EPC₀s were approximately equal to the SRPs, were in impermanent equilibrium with overlying water in status of phosphorus, the sediments can be likely to release phosphorus to the water column once the equilibrium was broken. Therefore, sedimentary phosphorus can be a secondary pollution source in downstream Nansi Lake.     

Particularités microstructurales du squelette de Paracentrotus lividus et Arbacia lixula: Rapports avec l'écologie et l'éthologie de ces échinoïdes

Scanning-electron-microscope investigations on the test microstructure of two regular sea urchins, Paracentrotus lividus (Lamarck) and Arbacia lixula Linné have been especially devoted to the sutures between test plates, and the spines. Some features of both these components may be related to ecological and ethological differences between the two species. It is well documented that the structure of the sea urchin's test plates consists of a meshwork of calcareous trabecules embedded within the mesenchyme. The suture between the two lines of plates of each radial or intertradial zone exhibits a gap which plays some part in the process of the plates' growth. However, the gap may also constitute a complementary stress-breaker of mechanical forces (such as waves) which are exerted upon the test in the natural environment. In A. lixula this gap is so wide and the height: diameter ratio so low, that this species is particularly well fitted to bear physical stress and force on its apical region: since A. lixula almost exclusively inhabits vertical or subvertical rocky substrates at 2 to 15 m depth, where wave action is mainly exerted perpendicular to the substrate, these particular features of sutures and test shape may be a morphofunctional adaptation to this habitat. The sutures of P. lividus exhibit a narrower gap, making this species less able to bear strong apical pressure; consequently, P. lividus usually occurs on exposed horizontal or gently inclined substrates, but also inhabits sea-grass beds as deep as 15 to 20 m. The spines of P. lividus bear deep longitudinal grooves with lateral teeth, which seem especially fitted for collecting and transporting organic particles from the top of the spines to the apical region of the test where they are digested and assimilated by coelomocytes and epithelial cells. In the natural environment, the slightest water motion provides the spines with suspended particles; in extremely sheltered places or in aquaria however, the spines actively collect particles. Therefore, P. lividus populations can thrive in places where food resources other than suspended particles are scarce. The grooves on the spines of A. lixula are less marked, and thus unsuitable for collection of suspended particles. This species can therefore fulfil its energy requirements only by grazing and absorption of dissolved material. It appears that although belonging to the same biocoenosis, P. lividus and A. lixula do not occupy the same ecological niche. Their potential utilization in either urban or chemical pollution monitoring studies is discussed.     

Using Coral Disease Prevalence to Assess the Effects of Concentrating Tourism Activities on Offshore Reefs in a Tropical Marine Park

Abstract: Concentrating tourism activities can be an effective way to closely manage high‐use parks and minimize the extent of the effects of visitors on plants and animals, although considerable investment in permanent tourism facilities may be required. On coral reefs, a variety of human‐related disturbances have been associated with elevated levels of coral disease, but the effects of reef‐based tourist facilities (e.g., permanent offshore visitor platforms) on coral health have not been assessed. In partnership with reef managers and the tourism industry, we tested the effectiveness of concentrating tourism activities as a strategy for managing tourism on coral reefs. We compared prevalence of brown band disease, white syndromes, black band disease, skeletal eroding band, and growth anomalies among reefs with and without permanent tourism platforms within the Great Barrier Reef Marine Park. Coral diseases were 15 times more prevalent at reefs with offshore tourism platforms than at nearby reefs without platforms. The maximum prevalence and maximum number of cases of each disease type were recorded at reefs with permanently moored tourism platforms. Diseases affected 10 coral genera from 7 families at reefs with platforms and 4 coral genera from 3 families at reefs without platforms. The greatest number of disease cases occurred within the spatially dominant acroporid corals, which exhibited 18‐fold greater disease prevalence at reefs with platforms than at reefs without platforms. Neither the percent cover of acroporids nor overall coral cover differed significantly between reefs with and without platforms, which suggests that neither factor was responsible for the elevated levels of disease. Identifying how tourism activities and platforms facilitate coral disease in marine parks will help ensure ongoing conservation of coral assemblages and tourism.     

Application of Laser Doppler Spectroscopy (LDS) in determining swimming velocities of motile phytoplankton

Pumping rates in Mytilus edulis L. were measured by means of a constant-level-tank method, in which hydrostatic pressure differences between inhalant and exhalant water levels were recorded by means of a laser beam reflected from a tethered mirror floating on the water surface. Hydrostatic pressure gradients were determined to ±0.05 mm H₂O or better. The developed technique of directly measuring pumping rates in mussels is not subject to the artefacts of other methods. The pumping rates measured in M. edulis were substantially higher than those previously determined by means of direct techniques, but similar to the maximum filtration rates, as obtained by means of two indirect techniques, i.e. about 50 ml min^-1 for a 0.15 g dry weight mussel. Positive hydrostatic pressures drastically affected water pumping. The pumping rate decreased linearly with increasing hydrostatic pressures towards a maximum pump pressure between 3 and 5 mm H₂O. Negative pressures only affected the pumping rate slightly or insignificantly, except when the mussels were exposed to rapidly increasing negative pressures. Under this condition a shunt was presumably established between the inner demibranchs, allowing water to bypass the gills.