• 010604 marine biology & hydrobiology close

Trophy hunting is one of the most controversial issues in the field of biodiversity conservation. In particular, proponents and opponents debate fiercely over whether it poses a threat to hunted populations. Here, we show that trophy hunting constitutes a greater menace to threatened species than previously realized. Because humans value rarity, targeted species that are threatened are likely to be disproportionately hunted, thereby becoming even more vulnerable, which could eventually push them to extinction. With the ten felid species currently hunted for their trophies, we present evidence that (1) the number of killed individuals increases with time, in several cases exponentially, despite population declines, (2) the price of trophies is strongly dependent on species protection status, (3) changes of protection status coincide with counter-intuitive changes of hunting pressures: protection intensification with augmented hunting effort, and protection relaxation with lower effort. This suggests an over-exploitation of trophy-hunted felids and the necessity of a better quota system coupled with reconsidered protection methods.

We performed a preliminary study to quantify CO2 and CH4 emissions from the water column within a Rhizophora spp. mangrove forest. Mean CO2 and CH4 emissions during the studied period were 3.35 +/- 3.62 mmolC m(-2) h(-1) and 18.30 +/- 27.72 mu molC m(-2) h(-1) , respectively. CO2 and CH4 emissions were highly variable and mainly driven by tides (flow/ebb, water column thickness, neap/spring). Indeed, an inverse relationship between the magnitude of the emissions and the thickness of the water column above the mangrove soil was observed. delta(CO2)-C-13 values ranged from -26.88 parts per thousand to -8.6 parts per thousand, suggesting a mixing between CO2-enriched pore waters and lagoon incoming waters. In addition, CO2 and CH4 emissions were significantly higher during ebb tides, mainly due to the progressive enrichment of the water column by diffusive fluxes as its residence time over the forest floor increased. Eventually, we observed higher CO2 and CH4 emissions during spring tides than during neap tides, combined to depleted delta(CO2)-C-13 values, suggesting a higher contribution of soil-produced gases to the emissions. These higher emissions may result from higher renewable of the electron acceptor and enhanced exchange surface between the soil and the water column. This study shows that CO2 and CH4 emissions from the water column were not negligible and must be considered in future carbon budgets in mangroves.

The condition and survival of Antarctic krill (Euphausia superba) strongly depends on sea ice conditions during winter. How krill utilize sea ice depends on several factors such as region and developmental stage. A comprehensive understanding of sea ice habitat use by krill, however, remains largely unknown. The aim of this study was to improve the understanding of the krill’s interaction with the sea ice habitat during winter/early spring by conducting large-scale sampling of the ice–water interface (0–2 m) and comparing the size and developmental stage composition of krill with the pelagic population (0–500 m). Results show that the population in the northern Weddell Sea consisted mainly of krill that were <1 year old (age class 0; AC0), and that it was comprised of multiple cohorts. Size per developmental stage differed spatially, indicating that the krill likely were advected from various origins. The size distribution of krill differed between the two depth strata sampled. Larval stages with a relatively small size (mean 7–8 mm) dominated the upper two metre layer of the water column, while larger larvae and AC0 juveniles (mean 14–15 mm) were proportionally more abundant in the 0- to 500-m stratum. Our results show that, as krill mature, their vertical distribution and utilization of the sea ice appear to change gradually. This could be the result of changes in physiology and/or behaviour, as, e.g., the krill’s energy demand and swimming capacity increase with size and age. The degree of sea ice association will have an effect on large-scale spatial distribution patterns of AC0 krill and on predictions of the consequences of sea ice decline on their survival over winter.

We hypothesize that phytoplankton have the sequential nutrient uptake strategy to maintain nutrient stoichiometry and high primary productivity in the water column. According to this hypothesis, phytoplankton take up the most limiting nutrient first until depletion, continue to draw down non-limiting nutrients and then take up the most limiting nutrient rapidly when it is available. These processes would result in the variation of ambient nutrient ratios in the water column around the Redfield ratio. We used high-resolution continuous vertical profiles of nutrients, nutrient ratios and on-board ship incubation experiments to test this hypothesis in the Strait of Georgia. At the surface in summer, ambient NO3− was depleted with excess PO43− and SiO4− remaining, and as a result, both N : P and N : Si ratios were low. The two ratios increased to about 10 : 1 and 0. 45 : 1, respectively, at 20 m. Time series of vertical profiles showed that the leftover PO43− continued to be removed, resulting in additional phosphorus storage by phytoplankton. The N : P ratios at the nutricline in vertical profiles responded differently to mixing events. Field incubation of seawater samples also demonstrated the sequential uptake of NO3− (the most limiting nutrient) and then PO43− and SiO4− (the non-limiting nutrients). This sequential uptake strategy allows phytoplankton to acquire additional cellular phosphorus and silicon when they are available and wait for nitrogen to become available through frequent mixing of NO3− (or pulsed regenerated NH4). Thus, phytoplankton are able to maintain high productivity and balance nutrient stoichiometry by taking advantage of vigorous mixing regimes with the capacity of the stoichiometric plasticity. To our knowledge, this is the first study to show the in situ dynamics of continuous vertical profiles of N : P and N : Si ratios, which can provide insight into the in situ dynamics of nutrient stoichiometry in the water column and the inference of the transient status of phytoplankton nutrient stoichiometry in the coastal ocean.

There is a pressing need to globally inventory and assess coastal and inland aquatic habitats; extremely valuable and productive regions that are vulnerable to global anthropogenic pressures and climatic change. Basic information about sessile communities (wetlands, coral reefs, and sea grasses) includes mapping their extent and distribution, which can be gleaned from spectral surface reflectance imagery at high spatial resolution, but moderate temporal resolution. Moderate to high temporal resolution is also required for detailed observations of sessile community change (e.g., phenology, disturbance) and high temporal resolution is required for environmental changes in the surrounding water, phytoplankton concentration and composition, and concentrations of sediment or chromophoric dissolved organic matter (CDOM). Current and upcoming satellite missions and technology could meet spatial and spectral challenges. Multiple orbiting and airborne platforms, along with a network of in situ measurements, could provide a more complete picture of how these vital resources are changing. This paper provides an overview of these resources.

A anestesia tem sido utilizada em aquicultura como técnica para facilitar a manipulação dos animais e amenizar o estresse causado pelos procedimentos de manejo. O presente estudo teve como objetivo determinar a eficiência de quatro fármacos como anestésico em juvenis de tainha Mugil liza. Os peixes (6,9 ± 1,4 g) foram submetidos individualmente (N=10 por concentração) í­Â anestesia utilizando-se quatro concentrações de benzocaí­­na (30, 40, 50 e 60 mg L-1), MS-222 (100, 125, 150 e 175 mg L-1), eugenol (50, 70, 90 e 110 mg L-1) e mentol (175, 200, 225 e 250 mg L-1). O critério utilizado para avaliação das melhores concentrações foi a faixa de tempo máximo de três e cinco minutos para anestesia e recuperação dos peixes respectivamente. As concentrações mais eficientes foram: benzocaí­­na, 50 mg L-1; MS-222, 150 mg L-1; eugenol, 70 mg L-1; e mentol, 225 mg L-1.

Abstract Benthic dinoflagellates of the toxigenic genus Coolia Meunier (Dinophyceae) are known to have a global distribution in both tropical and temperate waters. The type species, C. monotis, has been reported from the Mediterranean Sea, the NE Atlantic and from Rhode Island, USA in the NW Atlantic, whereas other species in the genus have been reported from tropical locations. Coolia cells were observed in algal drift samples collected at seven sites in Nova Scotia, Canada. Clonal isolates were established from four of these locations and identified with light and scanning electron microscopy, then confirmed with genetic sequencing to be C. monotis . This is the first record of this species in Nova Scotia. The isolates were established and incubated at 18 °C under a 14:10 L:D photoperiod with an approximate photon flux density of 50–60 μmol m −2 s −1 . Growth experiments using an isolate from Johnston Harbour (CMJH) were carried out at temperatures ranging from 5 to 30 °C under the same photoperiod with an approximate photon flux density of 45–50 μmol m −2 s −1 . Cells tolerated temperatures from 5 to 25 °C with optimum growth and mucilage aggregate production between 15 and 20 °C. Methanol extracts of this isolate examined by Liquid Chromatography-Mass Spectrometry (LC–MS) did not show the presence of the previously reported cooliatoxin. Toxic effects were assayed using two zebrafish bioassays, the Fish Embryo Toxicity (FET) assay and the General Behaviour and Toxicity (GBT) assay. The results of this study demonstrate a lack of toxicity in C. monotis from Nova Scotia, as has been reported for other genetically-confirmed isolates of this species. Conditions in which cell growth that could potentially degrade water quality and provide substrate and dispersal mechanisms for other harmful microorganisms via mucilage production are indicated.

Abstract The Ecosystem Approach to Management (EAM) has emerged over the past decades, largely to promote biodiversity conservation, and more recently sectoral tradeoffs in the management of marine ecosystems. To ascertain the state of practice of EAM operationalization, a workshop was held, which included a pre-workshop online survey. The survey gauged international participants’ perspectives regarding capacity, knowledge, and application of EAM. When asked about the subject, most survey respondents had a general understanding of EAM, and provided a clear definition. Major perceived challenges to EAM objectives by those surveyed included limited knowledge, conflicting interests, insufficient communication, and limited organizational legal frameworks or governance structures. Of those directly involved in an ecosystem approach, the majority responded that processes were in place or developed for application of integrated knowledge toward assessing key issues within their respective sectors (i.e. fisheries, conservation, energy), and that capacity was generally high. Our results show that most respondents, irrespective of sector or geography, see value in considering an integrated, broader ecosystem approach as they manage their sector. Although many participants were from the North Atlantic region, our results suggest that much of the international community is converging toward continued understanding of broad-scale, integrated approaches to marine resource management.

Abstract Accumulation of marine toxins in the organisms is one of the most important problems of the bivalve aquaculture. Mitigation methods are difficult to implement especially in species, as the mussel Mytilus galloprovincialis , which have a relatively low commercial value. For this species, one possible way of decreasing the toxin accumulation is to restrict the availability of toxic cells to the mussels by means of the reduction of the water flow around the perimeter of the culture ropes. We have checked the effectivity to decrease the accumulation of DSP toxins (okadaic acid) in mussels of two ways of obtaining that reduction: surrounding the ropes with a fishing net (1 cm mesh); and grouping the ropes (groups of four). During a four week period – with relatively high concentrations of particulate matter – those two ways were tested and shown to effectively reduce both, toxin concentration and toxin burden of cultured mussels exposed to toxic populations of Dinophysis acuminata . The observed reductions were important, 41% and 37% for grouping and surrounding with a net, respectively. Both methods can be used for mussel rafts and long lines and it is very likely they could be also effective with other kinds of toxicity and with other environmental conditions. Statement of relevance It would allow a substantial reduction of toxin accumulation.

Abstract Algal blooms threaten human health and aquatic ecosystem through the production of microcystins (MCs) by toxic strains. The accumulation of rare earth elements (REEs) in water affects the growth and physiological activities of algae. However, whether or how REEs affect cellular microcystins (MCs) is largely unknown. In this study, the effects of lanthanum ion [La(III)], a type of REE, on the MCs in Microcystis aeruginosa were investigated, and the mechanism of the effect was analyzed using ecological stoichiometry. The different concentrations of La(III) were selected to correlate environmental pollution status. Low-dose La(III) (0.2, 2.0, and 4.0 μM) exposure increased the total content of MCs and the percentage contents of microcystin-YR (MC-YR) and microcystin-LW (MC-LW) and decreased the percentage content of microcystin-LR (MC-LR). High-dose La(III) (8.0, 20, 40, and 60 μM) exposure decreased the total content of the MCs, increased the percentage content of MC-LR, and decreased the percentage contents of MC-YR and MC-LW. The changes in the total MCs content were positively associated with the ratios of C:P and N:P in algal cells. The composition of MCs was dependent on the ratio of C:N in algal cells; for example, the percentage content of MC-LR decreased and the percentage content of MC-YR and MC-LW increased as the ratio of C:N in algal cells increased. In conclusion, La(III) could affect the content and composition of MCs via changes in the growth and chlorophyll-a content of Microcystis aeruginosa, and these effects depended on the ratios of C:P, N:P, and C:N in Microcystis aeruginosa. Such changes may influence the toxicity of Microcystis blooms. The results provides a new insight into the mechanism of REEs effects on algal toxins and provide references for evaluating environmental risks of REEs pollution in aquatic ecosystems.