Anthropogenic electromagnetic fields (EMF) influence the behaviour of bottom-dwelling marine species.

Many marine animals have evolved sensory abilities to use electric and magnetic cues in essential aspects of life history, such as to detect prey, predators and mates as well as to orientate and migrate. Potential disruption of vital cues by human activities must be understood in order to mitigate potential negative influences. Cable deployments in coastal waters are increasing worldwide, in capacity and number, owing to growing demands for electrical power and telecommunications. Increasingly, the local electromagnetic environment used by electro- and magneto-sensitive species will be altered. We quantified biologically relevant behavioural responses of the presumed, magneto-receptive American lobster and the electro-sensitive Little skate to electromagnetic field (EMF) emissions of a subsea high voltage direct current (HVDC) transmission cable for domestic electricity supply. We demonstrate a striking increase in exploratory/foraging behaviour in skates in response to EMF and a more subtle exploratory response in lobsters. In addition, by directly measuring both the magnetic and electric field components of the EMF emitted by HVDC cables we found that there were DC and unexpectedly AC components. Modelling, restricted to the DC component, showed good agreement with measured results. Our cross-disciplinary study highlights the need to integrate an understanding of the natural and anthropogenic EMF environment together with the responses of sensitive animals when planning future cable deployments and predicting their environmental effects.

Preterm Premature Rupture of Membranes in Twins: Comparison of Rupture in the Presenting Versus Non-presenting Sac.

OBJECTIVE: This study sought to compare the latency from membrane rupture to delivery and subsequent neonatal outcomes in twin gestations complicated by preterm premature rupture of membranes (PPROM) of the presenting versus non-presenting sac. METHODS: This was a retrospective study of twin pregnancies over a 7-year period diagnosed with PPROM between 12 and 37 weeks gestation with a latency period to delivery of >24 hours. The ruptured sac was identified by ultrasound scan. The study compared the latency period from PPROM to delivery and subsequent neonatal morbidity and mortality resulting from rupture of the presenting versus non-presenting sac. Obstetric and neonatal outcomes were evaluated using a matched-cohort subset analysis (Canadian Task Force Classification II-2). RESULTS: During the study period, 77 twin pregnancies diagnosed with PPROM satisfied the inclusion criteria. The mean latency periods from PPROM to delivery were 10.1 days (n = 7) when the presenting sac ruptured and 41.3 days (n = 10) when the non-presenting sac ruptured (P < 0.05). Neonatal death was higher with PPROM of the presenting than the non-presenting sac (21.4% vs. 0%, respectively; P = 0.05). Neonates were more likely to be affected by retinopathy of prematurity (57% vs. 19%; P < 0.05) but less likely to have persistent pulmonary hypertension of the newborn (0% vs. 25%; P < 0.05) when the rupture occurred in the presenting sac. The rates of other neonatal adverse outcomes were similar between the two groups. CONCLUSIONS: In twin gestations there is a longer latency from PPROM to delivery and fewer neonatal complications when rupture occurs in the non-presenting rather than the presenting sac.

Buried Alive: The Behavioural Response of the Mussels, Modiolus modiolus and Mytilus edulis to Sudden Burial by Sediment.

Sedimentation in the sea occurs through natural processes, such as wave and tidal action, which can be exacerbated during storms and floods. Changes in terrestrial land use, marine aggregate extraction, dredging, drilling and mining are known to result in substantial sediment deposition. Research suggests that deposition will also occur due to the modern development of marine renewable energy. The response to individual burial under three depths of sediment, three sediment fractions and five burial durations was investigated in two mussel species, Modiolus modiolus and Mytilus edulis in specialist mesocosms. Both mussel species showed substantial mortality, which increased with duration of burial and burial by finer sediment fractions. M. modiolus was better able to survive short periods of burial than M. edulis, but at longer durations mortality was more pronounced. No mortality was observed in M. modiolus in burial durations of eight days or less but by 16 days of burial, over 50% cumulative mortality occurred. Under variable temperature regimes, M. edulis mortality increased from 20% at 8°C to over 60% at 14.5 and 20°C. Only M. edulis was able to emerge from burial, facilitated by increased byssus production, laid mostly on vertical surfaces but also on sediment particles. Emergence was higher from coarse sediment and shallow burials. Byssus production in M. edulis was not related to the condition index of the mussels. Results suggest that even marginal burial would result in mortality and be more pronounced in warm summer periods. Our results suggest that in the event of burial, adult M. modiolus would not be able to emerge from burial unless local hydrodynamics assist, whereas a small proportion of M. edulis may regain contact with the sediment water interface. The physiological stress resulting in mortality, contribution of local hydrodynamics to survival and other ecological pressures such as mussels existing in aggregations, are discussed.

Sediment Burial Intolerance of Marine Macroinvertebrates.

The marine environment contains suspended particulate matter which originates from natural and anthropogenic sources. Settlement of this material can leave benthic organisms susceptible to smothering, especially if burial is sudden i.e. following storms or activities such as dredging. Their survival will depend on their tolerance to, and their ability to escape from burial. Here we present data from a multi-factorial experiment measuring burial responses incorporating duration, sediment fraction and depth. Six macroinvertebrates commonly found in sediment rich environments were selected for their commercial and/or conservation importance. Assessments revealed that the brittle star (Ophiura ophiura), the queen scallop (Aequipecten opercularis) and the sea squirt (Ciona intestinalis) were all highly intolerant to burial whilst the green urchin (Psammichinus miliaris) and the anemone (Sagartiogeton laceratus), showed intermediate and low intolerance respectively, to burial. The least intolerant, with very high survival was the Ross worm (Sabellaria spinulosa). With the exception of C. intestinalis, increasing duration and depth of burial with finer sediment fractions resulted in increased mortality for all species assessed. For C. intestinalis depth of burial and sediment fraction were found to be inconsequential since there was complete mortality of all specimens buried for more than one day. When burial emergence was assessed O. ophiura emerged most frequently, followed by P. miliaris. The former emerged most frequently from the medium and fine sediments whereas P. miliaris emerged more frequently from coarse sediment. Both A. opercularis and S. laceratus showed similar emergence responses over time, with A. opercularis emerging more frequently under coarse sediments. The frequency of emergence of S. laceratus increased with progressively finer sediment and C. intestinalis did not emerge from burial irrespective of sediment fraction or depth. Finally, and perhaps unsurprisingly, the greatest ability to emerge from burial in all other species was from shallow (2 cm) burial. Although survival was consistently highly dependent on duration and depth of burial as expected, emergence behaviour was not as easily predictable thereby confounding predictions. We conclude that responses to burial are highly species specific and therefore tolerance generalisations are likely to be oversimplifications. These data may be used to inform environmental impact models that allow forecasting of the cumulative impacts of seabed disturbance and may provide mitigation measures for the sustainable use of the seabed.

The Influence of Organic Material and Temperature on the Burial Tolerance of the Blue Mussel, Mytilus edulis: Considerations for the Management of Marine Aggregate Dredging.

RATIONALE AND EXPERIMENTAL APPROACH: Aggregate dredging is a growing source of anthropogenic disturbance in coastal UK waters and has the potential to impact marine systems through the smothering of benthic fauna with organically loaded screening discards. This study investigates the tolerance of the blue mussel, Mytilus edulis to such episodic smothering events using a multi-factorial design, including organic matter concentration, temperature, sediment fraction size and duration of burial as important predictor variables. RESULTS AND DISCUSSION: Mussel mortality was significantly higher in organically loaded burials when compared to control sediments after just 2 days. Particularly, M. edulis specimens under burial in fine sediment with high (1%) concentrations of organic matter experienced a significantly higher mortality rate (p<0.01) than those under coarse control aggregates. Additionally, mussels exposed to the summer maximum temperature treatment (20°C) exhibited significantly increased mortality (p<0.01) compared to those in the ambient treatment group (15°C). Total Oxygen Uptake rates of experimental aggregates were greatest (112.7 mmol m-2 day-1) with 1% organic loadings in coarse sediment at 20°C. Elevated oxygen flux rates in porous coarse sediments are likely to be a function of increased vertical migration of anaerobically liberated sulphides to the sediment-water interface. However, survival of M. edulis under bacterial mats of Beggiatoa spp. indicates the species' resilience to sulphides and so we propose that the presence of reactive organic matter within the burial medium may facilitate bacterial growth and increase mortality through pathogenic infection. This may be exacerbated under the stable interstitial conditions in fine sediment and increased bacterial metabolism under high temperatures. Furthermore, increased temperature may impose metabolic demands upon the mussel that cannot be met during burial-induced anaerobiosis. SUMMARY: Lack of consideration for the role of organic matter and temperature during sedimentation events may lead to an overestimation of the tolerance of benthic species to smothering from dredged material.

Quorum sensing signal production and inhibition by coral-associated vibrios.

Corals are inhabited by complex communities of microbes that affect their growth and survival. Several studies suggest that coral disease may be attributed to the success of vibrios in out-competing other bacteria in the mucus and tissues of corals. Vibrios utilize a variety of quorum sensing (QS) signal molecules to regulate processes that could be used to colonize corals during adverse environmental conditions. We therefore screened a range of Vibrios isolated from a variety of healthy and diseased corals, for the production of the QS signal molecules, N-acylhomoserine lactones (AHLs) and the AI-2 (autoinducer-2) small furanone signal molecule. All 29 strains examined activated the AI-2 biosensor, but only 17 activated an AHL biosensor. Using reverse phase thin-layer chromatography, we showed that the effect of temperature on AHL production varied considerably among the isolates. For the first time, the QS inhibition by Vibrio harveyi is reported. This only occurred at higher temperatures and does not appear to be due to degradation of AHLs. The large diversity of vibrios and the different effects of temperature on signal production may partly explain the complexity of coral-associated community changes in response to environmental factors.