• Energy Research
• 14. Life underwater close
• CA close
• PLoS ONE close

In Eastern Boundary Upwelling Systems nutrient-rich waters are transported to the ocean surface, fuelling high photoautotrophic primary production. Subsequent heterotrophic decomposition of the produced biomass increases the oxygen-depletion at intermediate water depths, which can result in the formation of oxygen minimum zones (OMZ). OMZs can sporadically accumulate hydrogen sulfide (H2S), which is toxic to most multicellular organisms and has been implicated in massive fish kills. During a cruise to the OMZ off Peru in January 2009 we found a sulfidic plume in continental shelf waters, covering an area >5500 km(2), which contained ∼2.2×10(4) tons of H2S. This was the first time that H2S was measured in the Peruvian OMZ and with ∼440 km(3) the largest plume ever reported for oceanic waters. We assessed the phylogenetic and functional diversity of the inhabiting microbial community by high-throughput sequencing of DNA and RNA, while its metabolic activity was determined with rate measurements of carbon fixation and nitrogen transformation processes. The waters were dominated by several distinct γ-, δ- and ε-proteobacterial taxa associated with either sulfur oxidation or sulfate reduction. Our results suggest that these chemolithoautotrophic bacteria utilized several oxidants (oxygen, nitrate, nitrite, nitric oxide and nitrous oxide) to detoxify the sulfidic waters well below the oxic surface. The chemolithoautotrophic activity at our sampling site led to high rates of dark carbon fixation. Assuming that these chemolithoautotrophic rates were maintained throughout the sulfidic waters, they could be representing as much as ∼30% of the photoautotrophic carbon fixation. Postulated changes such as eutrophication and global warming, which lead to an expansion and intensification of OMZs, might also increase the frequency of sulfidic waters. We suggest that the chemolithoautotrophically fixed carbon may be involved in a negative feedback loop that could fuel further sulfate reduction and potentially stabilize the sulfidic OMZ waters.

Management regimes of marine resources that rely on spatial boundaries might be poorly adapted to climate change shifts in species distributions. This is of specific concern for the management of fish stocks that cross management jurisdictions, known as shared stocks. Transitioning to dynamic rules in spatial management has been suggested as a solution for mismatches between species distributions and the spatial boundaries. However, in many cases spatial boundaries are not clearly drawn, hampering such transitions. Here, we use black sea bass (Centropristis striata), summer flounder (Paralichthys dentatus) and scup (Stenotomus chrysops) as case studies to explore different approaches to designing spatial regulatory units to facilitate the adaptation of fisheries management to shifting distributions of shared stocks. First, we determine the yearly distribution of each stock within the United States Exclusive Economic Zone from 1951 to 2019 during Fall and Spring sampling seasons. Second, we explore two approaches for drawing regulatory units based on state waters and historical landings. Finally, we estimate each state’s proportion of the stock’s distribution and compare historical and recent values. We show that the distribution of all three stocks has changed relative to the years used to determine the current quota allocation across states, with an overall gain for central-northern states at the expense of the southernmost states. In terms of the distribution of allocation, we find that, while seasonal differences exist, the biggest differences in the proportion of the stock spatial distribution attributed to each state come from the method for designing regulatory units. Here, we show that the method used to define allocation units can have meaningful impacts on resulting adaptive policy. As climate change-driven conflicts in fishing resource allocation are expected to increase and deepen around the world, we provide a replicable approach to make an informed and transparent choice to support data-driven decision-making.

The responses of macroalgae to ocean acidification could be altered by availability of macronutrients, such as ammonium (NH4+). This study determined how the opportunistic macroalga, Ulva australis responded to simultaneous changes in decreasing pH and NH4+ enrichment. This was investigated in a week-long growth experiment across a range of predicted future pHs with ambient and enriched NH4+ treatments followed by measurements of relative growth rates (RGR), NH4+ uptake rates and pools, total chlorophyll, and tissue carbon and nitrogen content. Rapid light curves (RLCs) were used to measure the maximum relative electron transport rate (rETRmax) and maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm). Photosynthetic capacity was derived from the RLCs and included the efficiency of light harvesting (α), slope of photoinhibition (β), and the light saturation point (Ek). The results showed that NH4+ enrichment did not modify the effects of pH on RGRs, NH4+ uptake rates and pools, total chlorophyll, rETRmax, α, β, Fv/Fm, tissue C and N, and the C:N ratio. However, Ek was differentially affected by pH under different NH4+ treatments. Ek increased with decreasing pH in the ambient NH4+ treatment, but not in the enriched NH4+ treatment. NH4+ enrichment increased RGRs, NH4+ pools, total chlorophyll, rETRmax, α, β, Fv/Fm, and tissue N, and decreased NH4+ uptake rates and the C:N ratio. Decreased pH increased total chlorophyll content, rETRmax, Fv/Fm, and tissue N content, and decreased the C:N ratio. Therefore, the results indicate that U. australis growth is increased with NH4+ enrichment and not with decreasing pH. While decreasing pH influenced the carbon and nitrogen metabolisms of U. australis, it did not result in changes in growth.

Evaluating the efficacy of artificial structures in enhancing or sustaining biodiversity on tropical coral reefs is key to assessing their role in reef conservation or management. Here, we compare spatial and temporal patterns of colonization and succession of the benthic assemblage on settlement collectors (ceramic tiles) in a 13-mo mensurative experiment on a suspended artificial reef, a seafloor artificial reef, and two nearby natural reefs at Eilat, Gulf of Aqaba. We also conducted a concurrent 7-mo manipulative experiment on the suspended reef and one of the natural reefs, and monitored fish feeding behaviour on experimental collectors, to examine effects of large mobile consumers on these patterns. In both experiments, taxonomic composition as percent planar cover for the whole community or biomass for the invertebrate component differed between collector topsides, dominated by a filamentous algal matrix, and shaded undersides with a profuse assemblage of suspension- or filter-feeding invertebrates. In the mensurative experiment, we found differences in final community and invertebrate composition between sites, which clustered according to reef type (artificial vs. natural) for collector undersides. Invertebrate biomass was greater at both artificial reefs than at one (undersides) or both (topsides) natural reefs. In the manipulative experiment, we found similar differences in composition between sites/reef types as well as between treatments (exclusion vs. control), and the invertebrate biomass was greater on the artificial reef. Invertebrate biomass was greater in the exclusion treatment than the control on collector undersides, suggesting mobile consumers can affect community composition and abundance. Predominant fish species observed interacting with collectors differed between artificial and natural reefs, likely contributing to differences in patterns of colonization and succession between sites and reef types. Our findings suggest artificial reefs have the potential to enhance cover and biomass of certain reef-associated assemblages, particularly those occupying sheltered microhabitats.

Organisms provide some of the most sensitive indicators of climate change and evolutionary responses are becoming apparent in species with short generation times. Large datasets on genetic polymorphism that can provide an historical benchmark against which to test for recent evolutionary responses are very rare, but an exception is found in the brown-lipped banded snail (Cepaea nemoralis). This species is sensitive to its thermal environment and exhibits several polymorphisms of shell colour and banding pattern affecting shell albedo in the majority of populations within its native range in Europe. We tested for evolutionary changes in shell albedo that might have been driven by the warming of the climate in Europe over the last half century by compiling an historical dataset for 6,515 native populations of C. nemoralis and comparing this with new data on nearly 3,000 populations. The new data were sampled mainly in 2009 through the Evolution MegaLab, a citizen science project that engaged thousands of volunteers in 15 countries throughout Europe in the biggest such exercise ever undertaken. A known geographic cline in the frequency of the colour phenotype with the highest albedo (yellow) was shown to have persisted and a difference in colour frequency between woodland and more open habitats was confirmed, but there was no general increase in the frequency of yellow shells. This may have been because snails adapted to a warming climate through behavioural thermoregulation. By contrast, we detected an unexpected decrease in the frequency of Unbanded shells and an increase in the Mid-banded morph. Neither of these evolutionary changes appears to be a direct response to climate change, indicating that the influence of other selective agents, possibly related to changing predation pressure and habitat change with effects on micro-climate.

De nombreuses espèces se reproduisent lorsque les conditions sont les plus favorables à la survie des jeunes. De nombreux poissons et invertébrés intertidaux libèrent des œufs ou des larves pendant les marées nocturnes semi-lunaires de grande amplitude lorsque ces premiers stades de la vie sont les mieux à même d'échapper à la prédation par les poissons qui se nourrissent près du rivage pendant la journée. Fait remarquable, certaines espèces, dont les crabes violoneux Uca terpsichores et Uca deichmanni, maintiennent ce rythme tout au long de l'année, car la température, et donc le taux de développement embryonnaire, varient. Les mécanismes qui permettent une telle précision dans le moment de la production des jeunes sont mal connus. Une étude préliminaire a suggéré que lorsque la température diminue, les U. terpsichores s'accouplent plus tôt dans le cycle de l'amplitude des marées de sorte que les larves sont libérées au moment approprié. Nous avons testé cette idée en étudiant le moment de la parade nuptiale chez U. terpsichores et U. deichmanni car la température variait annuellement pendant deux ans, à 5 endroits qui différaient par la température du sédiment où les femelles incubent leurs œufs. Les Uca terpsichores courtisaient plus tôt aux endroits où la température des sédiments diminuait de façon saisonnière, mais pas là où la température des sédiments restait élevée tout au long de l'année. En revanche, des changements clairs dans le moment de la parade nuptiale n'ont pas été observés pour U. deichmanni malgré la variation de la température des sédiments. Nous discutons d'autres mécanismes par lesquels cette espèce peut maintenir le moment de la reproduction. Ces deux espèces sont susceptibles d'être affectées différemment par les changements de fréquence et d'intensité des périodes de froid qui devraient accompagner le changement climatique. Muchas especies se reproducen cuando las condiciones son más favorables para la supervivencia de los jóvenes. Numerosos peces e invertebrados intermareales liberan huevos o larvas durante las mareas nocturnas semilunares de gran amplitud cuando estas primeras etapas de la vida son más capaces de escapar de la depredación de los peces que se alimentan cerca de la costa durante el día. Sorprendentemente, algunas especies, incluidos los cangrejos violinistas Uca terpsichores y Uca deichmanni, mantienen este tiempo durante todo el año a medida que varía la temperatura y, por lo tanto, la tasa de desarrollo embrionario. Los mecanismos que permiten tal precisión en el momento de la producción de jóvenes son poco conocidos. Un estudio preliminar sugirió que cuando la temperatura disminuye, U. terpsichores se aparea más temprano en el ciclo de amplitud de las mareas, de modo que las larvas se liberan en el momento adecuado. Probamos esta idea estudiando el momento del cortejo en U. terpsichores y U. deichmanni a medida que la temperatura variaba anualmente durante dos años, en 5 ubicaciones que diferían en la temperatura del sedimento donde las hembras incuban sus huevos. Los terpsícoros de Uca cortejaron antes en lugares donde la temperatura de los sedimentos disminuyó estacionalmente, pero no donde la temperatura de los sedimentos permaneció elevada durante todo el año. Por el contrario, no se observaron cambios claros en el momento del cortejo para U. deichmanni a pesar de la variación en la temperatura del sedimento. Discutimos otros mecanismos por los cuales esta especie puede mantener el tiempo reproductivo. Es probable que estas dos especies se vean afectadas de manera diferente por los cambios en la frecuencia e intensidad de los períodos fríos que se espera que acompañen al cambio climático. Many species reproduce when conditions are most favorable for the survival of young. Numerous intertidal fish and invertebrates release eggs or larvae during semilunar, large amplitude, nocturnal tides when these early life stages are best able to escape predation by fish that feed near the shore during the day. Remarkably, some species, including the fiddler crabs Uca terpsichores and Uca deichmanni, maintain this timing throughout the year as temperature, and thus the rate of embryonic development, vary. The mechanisms that allow such precision in the timing of the production of young are poorly known. A preliminary study suggested that when temperature decreases, U. terpsichores mate earlier in the tidal amplitude cycle such that larvae are released at the appropriate time. We tested this idea by studying the timing of courtship in U. terpsichores and U. deichmanni as temperature varied annually during two years, at 5 locations that differed in the temperature of the sediment where females incubate their eggs. Uca terpsichores courted earlier at locations where sediment temperature declined seasonally but not where sediment temperature remained elevated throughout the year. In contrast, clear shifts in courtship timing were not observed for U. deichmanni despite variation in sediment temperature. We discuss other mechanisms by which this species may maintain reproductive timing. These two species are likely to be affected differently by changes in the frequency and intensity of cold periods that are expected to accompany climate change. تتكاثر العديد من الأنواع عندما تكون الظروف أكثر ملاءمة لبقاء الصغار. تطلق العديد من الأسماك واللافقاريات بين المد والجزر بيضًا أو يرقات خلال المد والجزر الهلالي، والسعة الكبيرة، والمد والجزر الليلي عندما تكون هذه المراحل المبكرة من الحياة أكثر قدرة على الهروب من الافتراس من قبل الأسماك التي تتغذى بالقرب من الشاطئ خلال النهار. ومن اللافت للنظر أن بعض الأنواع، بما في ذلك سرطانات Uca terpsichores و Uca deichmanni، تحافظ على هذا التوقيت على مدار العام حيث تختلف درجة الحرارة، وبالتالي معدل التطور الجنيني. والآليات التي تسمح بهذه الدقة في توقيت إنتاج الشباب غير معروفة. اقترحت دراسة أولية أنه عندما تنخفض درجة الحرارة، تتزاوج U. terpsichores في وقت مبكر من دورة اتساع المد والجزر بحيث يتم إطلاق اليرقات في الوقت المناسب. اختبرنا هذه الفكرة من خلال دراسة توقيت المغازلة في U. terpsichores و U. deichmanni حيث اختلفت درجة الحرارة سنويًا خلال عامين، في 5 مواقع اختلفت في درجة حرارة الرواسب حيث تحضن الإناث بيضها. ترابطت Uca terpsichores في وقت سابق في المواقع التي انخفضت فيها درجة حرارة الرواسب موسمياً ولكن ليس حيث ظلت درجة حرارة الرواسب مرتفعة على مدار العام. على النقيض من ذلك، لم يتم ملاحظة تحولات واضحة في توقيت المغازلة لـ U. deichmanni على الرغم من التباين في درجة حرارة الرواسب. نناقش الآليات الأخرى التي يمكن من خلالها لهذا النوع الحفاظ على توقيت التكاثر. من المرجح أن يتأثر هذان النوعان بشكل مختلف بالتغيرات في تواتر وشدة الفترات الباردة التي من المتوقع أن تصاحب تغير المناخ.