Photic Entrainment of Circadian Activity Patterns in the Tropical Labrid Fish Halichoeres chrysus

Yellow wrasses (Halichoeres chrysus) show clear daily activity patterns. The fish hide in the substrate at (subjective) night, during the distinct rest phase. Initial entrainment in a 12h:12h light-dark (12:12 LD) cycle (mean period 24.02h, SD 0.27h, n = 16) was followed by a free run (mean period 24.42h, SD 1.33h) after transition into constant dim light conditions. Light pulses of a comparable intensity as used in the light part of the LD cycles did not result in significant phase shifts of the free-running rhythm in constant darkness. Application of much brighter 3h light pulses resulted in a phase-response curve (PRC) for a fish species, with pronounced phase advances during late subjective night. The PRCs differed from those mainly obtained in other vertebrate taxa by the absence of significant phase delays in the early subjective night. At that circadian phase, significant tonic effects of the light pulses caused a shortening of the circadian period length. Entrainment to skeleton photoperiods of 1:11 LD was observed in five of six wrasses exposed, also after a 3h phase advance of this LD cycle. Subsequently, a 1:11.25 LD cycle resulted in entrainment in four of the six fish. It is suggested that the expression of the circadian system in fish can be interpreted as a functional response to a weak natural zeitgeber, as present in the marine environment. This response allows photic entrainment as described here in the yellow wrasse.

Mechanical ventilation-induced intrathoracic pressure distribution and heart-lung interactions

OBJECTIVE: Mechanical ventilation causes cyclic changes in the heart's preload and afterload, thereby influencing the circulation. However, our understanding of the exact physiology of this cardiopulmonary interaction is limited. We aimed to thoroughly determine airway pressure distribution, how this is influenced by tidal volume and chest compliance, and its interaction with the circulation in humans during mechanical ventilation. DESIGN: Intervention study. SETTING: ICU of a university hospital. PATIENTS: Twenty mechanically ventilated patients following coronary artery bypass grafting surgery. INTERVENTION: Patients were monitored during controlled mechanical ventilation at tidal volumes of 4, 6, 8, and 10 mL/kg with normal and decreased chest compliance (by elastic binding of the thorax). MEASUREMENTS AND MAIN RESULTS: Central venous pressure, airway pressure, pericardial pressure, and pleural pressure; pulse pressure variations, systolic pressure variations, and stroke volume variations; and cardiac output were obtained during controlled mechanical ventilation at tidal volume of 4, 6, 8, and 10 mL/kg with normal and decreased chest compliance. With increasing tidal volume (4, 6, 8, and 10 mL/kg), the change in intrathoracic pressures increased linearly with 0.9 ± 0.2, 0.5 ± 0.3, 0.3 ± 0.1, and 0.3 ± 0.1 mm Hg/mL/kg for airway pressure, pleural pressure, pericardial pressure, and central venous pressure, respectively. At 8 mL/kg, a decrease in chest compliance (from 0.12 ± 0.07 to 0.09 ± 0.03 L/cm H2O) resulted in an increase in change in airway pressure, change in pleural pressure, change in pericardial pressure, and change in central venous pressure of 1.1 ± 0.7, 1.1 ± 0.8, 0.7 ± 0.4, and 0.8 ± 0.4 mm Hg, respectively. Furthermore, increased tidal volume and decreased chest compliance decreased stroke volume and increased arterial pressure variations. Transmural pressure of the superior vena cava decreased during inspiration, whereas the transmural pressure of the right atrium did not change. CONCLUSIONS: Increased tidal volume and decreased chest wall compliance both increase the change in intrathoracic pressures and the value of the dynamic indices during mechanical ventilation. Additionally, the transmural pressure of the vena cava is decreased, whereas the transmural pressure of the right atrium is not changed

Stemming Decline of the Coastal Ocean: Rethinking Environmental Management

A Policy Brief from the United Nations University, International Network on Water, Environment and Healthlink_to_OA_fulltex

Strengthening Coastal Pollution Management in the Wider Caribbean Region

Control of aquatic pollution is critical for improving coastal zone management and for the conservation of fisheries resources. Countries in the Wider Caribbean Region (WCR) generally lack monitoring capacity and do not have reliable information on the levels and distribution of pollutants, particularly chemical contaminants, and the ecological and/or human health risks. Given the substantial cultural and economic importance of coastal environments to WCR communities, this should be cause for serious concern. This paper describes two studies determining persistent organic pollutants (POPs) in 1) the white grunt fish (Haemulon plumieri) and 2) three oyster species. It highlights lessons learned on improving capacity for environmental monitoring of POPs and how to build an effective south-south network involving academic institutions, laboratories and management agencies. Data are reported for Jamaica, St. Lucia, Trinidad and Tobago, Belize, and the Caribbean coast of Mexico. Overall, PCB and organochlorine concentrations were low relative to consumption guidelines used to protect the health of humans consuming contaminated seafood. However, since both monitoring organisms occupy low to mid-trophic levels in the marine food web, there is a risk of higher contaminant concentrations accumulating in top trophic levels, such as piscivorous fish and birds. Identified sources of contaminants include domestic sewage, agriculture and industry, large continental rivers and atmospheric deposition. For example, data indicate that atmospheric deposition is a likely source of POPs in Belize, while there is evidence of point sources of POPs in St. Lucia. Currently, these are the only data available on POPs contamination in fish and oysters distributed across the WCR, but will hopefully lead to future studies, increased awareness and strengthening of coastal pollution managemen

The growing need for sustainable ecological management of marine communities of the Persian Gulf

The Persian Gulf is a semi-enclosed marine system surrounded by eight countries, many of which are experiencing substantial development. It is also a major center for the oil industry. The increasing array of anthropogenic disturbances may have substantial negative impacts on marine ecosystems, but this has received little attention until recently. We review the available literature on the Gulf's marine environment and detail our recent experience in the United Arab Emirates (U.A.E.) to evaluate the role of anthropogenic disturbance in this marine ecosystem. Extensive coastal development may now be the single most important anthropogenic stressor. We offer suggestions for how to build awareness of environmental risks of current practices, enhance regional capacity for coastal management, and build cooperative management of this important, shared marine system. An excellent opportunity exists for one or more of the bordering countries to initiate a bold and effective, long-term, international collaboration in environmental management for the Gulf. © Royal Swedish Academy of Sciences 2010

Preserving Reef Connectivity: a Handbook for Marine Protected Area Managers

The decline of the coastal ocean and why this handbook exists:\ud \ud The coastal ocean environment provides enormous value in fishery and other products, as well as ecosystem services like coastal protection, water purification, and locations for ports, harbors, urban centers, tourist destinations, and numerous recreational pursuits. Coastal environments can also cleanse the soul, stimulate the mind, and restore the body. But 40% of all people live within 50 km of a coast, and our enthusiasm for coastal living is creating ever more environmental damage.\ud \ud Unfortunately, current management practices in most coastal regions are ineffective, and to continue them will endanger the coastal economies and ecosystems that support over one half of the world’s population. The trend for coastal ocean ecosystems over recent decades has been one of progressive decline in the face of growing human population, rising demand for coastal resources, and increasing use of the coastal environment. Today, climate change is adding to the\ud pressures on the coastal environment, further stressing ecosystems there.\ud \ud The decline of coastal environments has become a particularly significant problem for many tropical countries with coral reefs. In these areas, reefs often contribute to the major component of GDP because of their importance to tourism and fisheries. They also provide an important protein food source and help support a traditional way of life for coastal peoples.\ud \ud This handbook tackles one specific concern when contemplating effective management of coastal marine environments – the issue of connectivity. Marine protected areas (MPAs) have become an important management tool, particularly in tropical regions, and connectivity is an important consideration in the effective design of MPAs and MPA networks. Connectivity issues are also\ud involved in most other aspects of coastal management for two reasons: first, water moves and transports items such as sediments, nutrients and pollutants considerable distances; and second, most marine organisms also move within the water stream, transporting themselves between\ud places. Our goal is to assist MPA managers and others in understanding and applying the concept of connectivity in their work. In this way, we hope to help managers strengthen their ability to tackle the challenging task of sustaining coastal marine environments. This would help protect fisheries and other goods and services they provide