Physiological Responses of Pelagic Sargassum (Phaeophyceae) to Thermal Stress Vary by Species and Morphotype

This study aims to investigate diurnal sea surface temperature (SST) rise in Mutsu Bay, and its relationship with the local atmospheric field. First, the characteristics of diurnal SST warming is revealed, using satellite and buoy data during 1995-2000. Satellite observations can clearly capture large diurnal SST rise that reaches a few degrees, and clarify the spatial distribution of the SST rise. The diurnal variation of the satellite-derived SST will reflect that of skin SST, which is defined as the temperature of the top layer with the thickness of a few tens micrometers. The analysis of the bulk SST observed with buoys at 1-m depth reveals that the frequency of large diurnal amplitude of SST (ΔSST) appearance becomes high from April to August, and the bulk ΔSST exceeds 1.0 K in some places in the bay for 71% of the days in July. Over the bay, surface air temperature in the daytime is higher than the bulk SST on average in April-August. From spring to summer the wind becomes weaker, and the easterly wind becomes frequent. The weak wind plays a role in promoting the diurnal SST rise, and the warm air-temperaturemay also secondarily contribute to large ΔSST.A model experiment is then performed to examine a local atmospheric circulation that develops around the bay under a clear and calm condition in summer, and to address the interaction between the circulation, and the diurnal SST warming. A local circulation forced by the land surface solar heating of this area produces the weak easterly surface wind and the subsidence of the air, and makes the air warmer over the bay. This is consistent with the observational results. In such a case, the diurnal rise of skin SST simulated by an ocean model exceeds 2 K all over the bay, and it is especially large in the northeastern area. If the diurnal skin SST rise is considered in the atmospheric model, although the circulation pattern does not change, the circulation becomes weaker and the surface air temperature increases. This result suggests that the diurnal SST variation will be important for the practical prediction of air temperature in coastal areas.

Pollen-based quantitative reconstructions of Holocene climate at Gun Nuur in the northern Mongolian Plateau

Background. Climate change concurrent with anthropogenic disturbances can initiate serial changes that reverberate up the food chain with repercussions for fisheries. To date, there is no information available concerning the combined effects of global warming and human impacts on tropical marine food webs. While temperate copepods respond differently to warming and environmental stressors, the extent to which tropical copepods can adapt to rising temperature of already warm waters remains unknown. We hypothesize that sea warming and other anthropogenic disturbances over the long term will have the greatest impact on the copepod community in nearshore waters where their effects are accentuated, and therefore vulnerable and resilient species could be identified.Methods. Zooplankton samples were collected during two time periods (1985–86 and 2014–15) interposed by marked anthropogenic disturbances, and at the same five stations located progressively from inshore to offshore in Klang Strait, Malaysia, following the asymmetrical before-after-control-impact (BACI) design. Copepods were identified to species, and results were interpreted by univariate (ANOVA) and multivariate (PERMANOVA, PCO) analyses of the computed species abundance and diversity measures.Results. Copepod total abundance was not significantly different among stations but higher after disturbance than before disturbance. However, changes in the abundance of particular species and the community structure between time periods were dramatic. Coastal large-bodied calanoid species (e.g., Acartia spinicauda, Calanopia thompsoni, Pseudodiaptomus bowmani and Tortanus forcipatus) were the most vulnerable group to disturbance. This however favored the opportunistic species (e.g., Oithona simplex, O. attenuata, Hemicyclops sp., Pseudomacrochiron sp. and Microsetella norvegica). Small-bodied copepods (e.g., Paracalanus sp., Parvocalanus crassirostris and Euterpina acutifrons) were unaffected. Centropages tenuiremis was likely an introduced species. There was no significant loss in species richness of copepods despite the dramatic changes in community structure.Discussion. Sea warming and other human-induced effects such as eutrophication, acidification and coastal habitat degradation are likely the main factors that have altered copepod community structure. The large-bodied estuarine and coastal calanoid copepods are surmised to be vulnerable to eutrophication and hypoxia, while both resilient and opportunistic species are largely unaffected by, or adaptable to, degraded coastal environments and observed sea surface temperature (SST) rise. It is forecasted that SST rise with unmitigated anthropogenic impacts will further reduce large-bodied copepod species the favoured food for fish larvae with dire consequences for coastal fish production.

Coral reefs are very sensitive and vulnerable to Sea Surface Temperature (SST) rise than their optimal maximum temperature (27°C). SST rise do not only affect coral reef but also fishery production. Line Intersect Transect (LIT) and key informant interview have been used to study the effect of SST on coral reefs in Chole bay and Jibondo in Mafia Island. Sea Surface temperature in Mafia has increased by 0.56°C since 2001 up to 2016. This increase has significant effect on coral reef health, as it causes coral bleaching and reduction of fish catch. In Mafia Island increase in SST from November 2015 up to April 2016 was exacerbated by El Nino incidence in the Indian Ocean. The El Nino incidence was very strong with the temperature rise of 2.3°C. Almost 50% of coral reefs in Mafia have been bleached in 2016 while from 2001 bleaching varied in yearly basis. That's, coral reefs tend to bleach from January to March in every year and recover from September to November in every year, but the 2016 bleaching incidence was very severe since, 40-60% was bleached in mafia Island.

The influence of the sea surface temperature (SST) rise on extratropical baroclinic instability wave activity is investigated using an aquaplanet general circulation model (GCM). Two types of runs were performed: the High+3 run, in which the SST is increased by 3 K only at high latitudes, and the All+3 run, in which the SST is increased uniformly by 3 K all over the globe. These SST rises were intended to reproduce essential changes of the surface air temperature due to global warming. Wave activity changes are analyzed and discussed from the viewpoint of the energetics. In the High+3 run, midlatitude meridional temperature gradient is decreased in the lower troposphere and the wave energy is suppressed in the extratropics. In the All+3 run, although the large tropical latent heat release greatly enhances the midlatitude meridional temperature gradient in the upper troposphere, global mean wave energy does not change significantly. These results suggest that the low-level baroclinicity is much more important for baroclinic instability wave activity than upper-level baroclinicity. A poleward shift of wave energy, seen in global warming simulations, is evident in the All+3 run. Wave energy generation analysis suggests that the poleward shift of wave activity may be caused by the enhanced and poleward-shifted baroclinicity in the higher latitudes and the increased static stability in the lower latitudes. Poleward expansion of the high-baroclinicity region is still an open question.

In the present work, we have evaluated the satellite estimated daily downwelling shortwave (QI) and Longwave (QA) radiation from Moderate Resolution Imaging Spectrometer (MODIS) /Clouds and the Earth's Radiant Energy System (CM) with moored buoy observations of Global Tropical Moored Buoy Array (GTMBA) during 2001-2009. The global observed mean of QI and QA in GTMBA (CM) are 228 (233) W/m2 and 410 (405) W/m2 respectively. The mean QI shows a positive bias (~3- 7 W/m2) whereas QA underestimates with a mean negative bias of ~3-6 W/m2 in the tropical Pacific, Atlantic and Indian Ocean. CM underestimates the buoy observed variability in both QI and QA in all the tropical oceans. The correlation coefficient (CC) values in QI (Qa) are 0.79(0.88) 0.79(0.84) and 0.81(0.94) over the Pacific, Atlantic and Indian ocean respectively. The Root Mean Square Error (RMSE) values in QI ranged between 35-43 W/m2 with lowest values in the Atlantic Ocean and highest in the Indian Ocean. The RMSE values in QA are less as compared to QI and it is ~9 W/m2 in all the tropical ocean. The spatial distributions of QI and QA shows seasonality with lower and higher values coinciding with the Inter Tropical Convergence Zone(ITCZ) locations in the QI and QA.

Impacts of climate change and sea-level rise on cyclonic storm surge floods in Bangladesh

The response of the polar atmosphere to the reduction of sea ice area in the Arctic and the rise of sea surface temperature is considered using the atmospheric general circulation model with prescribed boundary conditions on the ocean surface. Boundary conditions include the observed sea ice concentration and the sea surface temperature in recent three decades. The study demonstrates that the reduction of sea ice extent is the major factor contributing to the amplification of the warming in the Arctic. However, the spatiotemporal distribution of the warming is not uniform. It is mostly pronounced in autumn and winter and extends up to the height of about 1 km in the areas of large reduction of sea ice concentration or of its complete disappearance. It is demonstrated that the rise of the sea surface temperature also provides some contribution to the warming in the Arctic. Due to the global warming in recent decades statistically significant changes occurred in the distribution of the sea-level pres sure and geopotential heights in the polar region and at mid-latitudes in autumn, winter, and spring. However, these changes are mainly associated with the increase in the sea surface temperature but not with the reduction of sea ice extent. The study has not revealed any significant ret ationships between ice cover anomalies in the Arctic and the evolution of pressure patterns of the synoptic scale that could contribute to the development of cold weather episodes over Eurasia in winter.

Rising temperatures and altered nutrient supply are expected to influence future phytoplankton thermal performance and community dynamics. The thermal response of phytoplankton has been shown to be influenced by nutrient availability, but information is still limited, particularly for the coastal Southern Ocean. Additionally, environmental interactions are often tested with single species but rarely address comparisons between populations and communities. To fill this gap, we experimentally investigated the thermal response in maximum growth rate (μmax), carrying capacity (K) and stoichiometry of three Antarctic phytoplankton species (Chaetoceros simplex, Geminigera cryophila, and Phaeocystis antarctica) in interaction with three nitrogen : phosphorus (N : P) ratios and identified the thermal traits of each species in monocultures and a mixed assemblage. Phytoplankton growth rate (μmax) showed a typical unimodal response to temperature with a thermal optimum around 4°C and significantly higher μmax with nutrient addition. The strongest temperature sensitivity to nutrient supply was observed around Topt and an ambient N : P supply ratio. Thermal traits, however, showed only minor changes with nutrient supply, indicating saturated nutrient concentrations. Nutrient addition significantly increased K while the thermal response of K was constant. Phytoplankton N : P was species‐specific and significantly altered by the temperature × nutrient interaction. Species‐specific growth performance varied whether the species grew in monocultures or in communities, demonstrating that monoculture thermal performance does not necessarily predict species thermal responses in multispecies assemblages. Overall, the results indicate that increasing temperatures will push Antarctic phytoplankton closer to their thermal optimum, altering phytoplankton growth, stoichiometry, and species interactions.

[1] This study investigates the climatological and changing characteristics of tropical rain and cloud systems in relation to sea surface temperature (SST) changes using Tropical Rainfall Measuring Mission (TRMM) data (1998–2009). Rainfall and cloud characteristics are determined from probability distribution functions (pdf), derived from daily TRMM Microwave Imager (TMI) and Precipitation Radar (PR) surface rain, Visible and Infrared Scanner (VIRS) brightness temperature (Tb), and PR echo top height (HET). Results show that the top 10% heavy rain is associated with cold cloud tops (Tb 6 km), associated with ice phase rain in the Intertropical Convergence Zone and monsoon regions. The bottom 5% light rain occurs most frequently in the subtropics and also in the warm pool regions with low cloud top (Tb > 273 K) and HET ∼ 1–4 km. Intermediate rain (25th to 75th percentile) is contributed by a wide range of middle clouds and mixed-phase rain centered at Tb ∼ 230–260 K and HET ∼ 4–6 km within the warm pool. The relationships between rainfall and SST depend strongly on rain types. We find that a warmer tropical ocean favors a large increase in annual heavy rain accumulation, a mild reduction in light to moderate rain, and a slight increase in extremely light rain. The annual accumulation of extreme heavy rain increases approximately 80%–90% for every degree rise in SST, much higher than that expected from the Clausius-Clapeyron equation for global water balance. This is possibly because heavy rain is only a component of the tropical water cycle and is strongly associated with ice phase processes and convective dynamics feedback.

The geographical range of schistosomiasis is affected by the ecology of schistosome parasites and their obligate host snails, including their response to temperature. Previous models predicted schistosomiasis' thermal optimum at 21.7°C, which is not compatible with the temperature in sub-Saharan Africa (SSA) regions where schistosomiasis is hyperendemic. We performed an extensive literature search for empirical data on the effect of temperature on physiological and epidemiological parameters regulating the free-living stages of S. mansoni and S. haematobium and their obligate host snails, i.e., Biomphalaria spp. and Bulinus spp., respectively. We derived nonlinear thermal responses fitted on these data to parameterize a mechanistic, process-based model of schistosomiasis. We then re-cast the basic reproduction number and the prevalence of schistosome infection as functions of temperature. We found that the thermal optima for transmission of S. mansoni and S. haematobium range between 23.1-27.3°C and 23.6-27.9°C (95% CI) respectively. We also found that the thermal optimum shifts toward higher temperatures as the human water contact rate increases with temperature. Our findings align with an extensive dataset of schistosomiasis prevalence in SSA. The refined nonlinear thermal-response model developed here suggests a more suitable current climate and a greater risk of increased transmission with future warming for more than half of the schistosomiasis suitable regions with mean annual temperature below the thermal optimum.

Using satellite‐based cloud measurements for 1984–2004, the interannual variability of the low‐level cloud cover over the tropical Atlantic Ocean in austral winter (June–July–August, JJA) is examined. It is found that the leading pattern of the low‐cloud anomalies in this season is a modulation of the climatological center of the cloud cover over the southeastern tropical Atlantic Ocean off the Angola and Namibia coasts. The fluctuation of cloud amount there occurs on both interannual and longer timescales. The relationship between this low‐cloud anomalous pattern and basinwide ocean‐atmosphere anomalies is studied through a composite analysis based on the objectively selected major low‐cloud deficit and excess years. For the composites we intentionally use data sets mainly based on satellite measurements for the past one to two decades to minimize the potential influences of the bias in the model‐based ocean‐atmosphere analyses. The composites show that the JJA anomalous cloud pattern is strongly influenced by the sea surface temperature (SST) anomalies of the equatorial and southeastern tropical Atlantic Ocean in the previous summer. The anomalous surface warm events off the southwestern coast of Africa near 15°S in January and February are usually initiated dynamically by remote forcing from the westerly wind anomalies over the western equatorial Atlantic, preceding the cloud anomalies. During the next few months, the warm water is spread into the southeastern tropical Atlantic Ocean and is conducive to deficit low‐cloud cover in subsequent JJA. The reduced low‐cloud cover in turn forces positive SST tendency in a larger area of the southeastern Atlantic Ocean by changing the amount of the local solar radiation reaching the sea surface. In June and July, this process moves the major center of the SST anomalies away from the coast and closer to the equator when the coastal process weakens. The low cloud‐radiation‐SST feedback also plays a role in the slow westward expansion of the SST anomalies in late austral winter and spring. Overall, the influence of the cloud fluctuation is an important component in the evolution of the southeastern tropical Atlantic anomalous events.

An analysis was made of (i) the annual sea-surface temperature in the northern North Atlantic; (ii) the sea temperatures (0–200 m) along 33°00′E between 70°30′ and 72°30′N (Kola Section) representative of the inflow of relatively warm North Atlantic water into the Barents Sea; and (iii) the annual air temperatures and pressures over the northern North Atlantic, Greenland, and Europe to determine whether the ocean lags (behind) the atmosphere during a climatic change by comparing the 1951–60 decade with the preceding 1941–50 decade, and with the 1921–50 period as a whole; and the 1961–70 decade with the preceding 1951–60 decade. The results obtained show a decline in the air temperature with no change in the sea-surface temperature in the 1951–60 decade from the preceding 1941–50 decade, and a rise in sea-surface temperature in the 1951–60 decade over the 1921–50 period suggesting a lag in the ocean vis-a-vis the atmosphere. The results further show a decrease in both the sea and air temperatures ...

Mangrove increases resiliency of the French Guiana shrimp fishery facing global warming

The Arctic marine environment is rapidly changing with rising sea surface temperatures, declining sea ice habitat and projected increases in boreal species invasions. The success of resident Arctic fish will depend on both their thermal tolerance and their ability to cope with changing trophic interactions. Larval fish energetic condition is closely associated with mortality rates and therefore provides an indicator of overall well-being or fitness. In this study, we experimentally determined larval morphometric and lipid-based condition in an Arctic gadid (Arctic cod, Boreogadus saida) and a boreal gadid (walleye pollock, Gadus chalcogrammus) in response to different temperatures and food rations. Our results suggest that larval condition is highly sensitive to both factors but varies in a species- and ontogenetic-dependent manner. Results indicated that condition metrics based on length–weight relationships were not as sensitive as those based on lipid storage. Further, condition metrics changed with ontogeny and were best used within a developmental stage rather than across developmental stages. As expected, larval condition in first-feeding Arctic cod was higher at colder temperatures (2–5°C) than in the boreal gadid (5–12°C). However, at more developed larval stages the peak condition for Arctic cod was at warmer temperatures (7°C), while walleye pollock had the same thermal optimum as during earlier stages. Arctic cod were more sensitive to food ration at first feeding than walleye pollock, however; at later larval stages both species had a negative condition response to low food ration, especially at elevated temperatures (5 vs. 7°C). The lower thermal tolerance of Arctic cod, coupled with a higher sensitivity to food availability indicates that Arctic cod are particularly vulnerable to on-going environmental change. Arctic cod is a lipid-rich keystone species and therefore a reduction in their energetic condition during summer has the potential to affect the health of higher trophic levels throughout the Alaskan Arctic.