Connectivity between coastal habitats of two oceanic Caribbean islands as inferred from ontogenetic shifts by coral reef fishes

Mangroves and seagrass beds are considered important nursery habitats for juveniles of coral reef fishes. Studies have mostly focused on the fish community of just one habitat, so the connectivity between different coastal habitats is often unclear. In this study, density and size of reef fish were determined using a single sampling technique in four non-estuarine bay habitats and four reef zones in Curaçao and Bonaire (Netherlands Antilles). The data indicate that of the complete reef fish community at least 21 species show ontogenetic crossshelf shifts in habitat utilization. The 21 species mainly utilized shallow-water habitats (mangroves, seagrass beds, channel and shallow reef) as nursery habitats and the deeper coral reef zones (\u3e 5 m depth) as adult lifestage habitats. Fish species utilized 1–3 different nursery habitats simultaneously, but habitat utilization clearly differed between species. Previous studies showed that the dependence on these nursery habitats is very high, based on reduced density or absence of adults on coral reefs where these habitats were absent. The strong connectivity between several coastal habitats during the ontogeny of various commercially important reef fish species is evidence for the inclusion of bay habitats within boundaries of fishery reserves or marine protected areas

The Acquisition of a Memory Phenotype by Murine CD4+ T Cells Is Accompanied by a Loss in Their Capacity to Increase Intracellular Calcium

During the process of aging, the fraction of CD4+ T Cells with a naive phenotype, that is, Pgp-1- CD45RBHighMEL-14+, decreases in favor of CD4+ T memory cells. Total CD4+ T cells from aged mice displayed a diminished calcium response to anti-CD3 and even ionomycin as compared to the cells from young mice, and this was related to the changed composition of the CD4+ T-cell population. Regardless the age of the donor mice, naive CD4+ T cells effectively increased intracellular calcium, whereas memory CD4+ T cells were impaired in this regard. In addition, a heterogeneity in the differentiation stage of the naive CD4+ T cells was shown by the observation that calcium mobilization in naive CD4+ T cells from young mice was more profound than that in their aged counterparts. These data thus indicate that during the acquisition of a memory phenotype, murine CD4+ T cells lose the capacity to increase intracellular calcium, which in turn may be responsible for the decreased level of IL-2 production by these cells

Chapter 5 Consequences of Anthropogenic Changes in the Sensory Landscape of Marine Animals

Human activities are altering a wide range of key marine cues at local and global scales, and it is important to know how animals may respond. Species survival and performance depend on the ability of individuals to successfully extract and interpret information from their environment about preferred abiotic conditions and the presence of prey, predators, competitors, mates and suitable habitats. Such information is made available via a wide range of abiotic and biotic cues that can be detected by organisms through various sensory modalities. Global anthropogenic changes, however, are rapidly altering the sensory landscape (‘cuescape’) and behaviour of animals by modifying the production, transmission and interpretation of critical natural cues, as well as introducing novel anthropogenic cues. To date, most studies have focussed on how animals respond to such changes rather than investigating how the cues themselves are changing. Because the responses that individuals show ultimately depend on factors affecting both the generation and reception of cues, better integration is needed to understand how these factors ultimately affect individual performance. This review provides a holistic assessment of how multiple cues (e.g. sounds, visual cues, chemicals, salinity, temperature and electromagnetism) are being altered at different spatial and temporal scales in marine habitats. Natural cuescapes are being modified by humans and novel anthropogenic cues are being introduced into the ocean, both of which can directly and indirectly alter the diversity and strength of natural cues. Examples are provided of how species might respond to such changes, focussing on what coping and adaptation mechanisms are available for species to persist in a future ocean. While ‘sensory generalist’ species may prevail in marine environments with diminishing or masked natural cues, some ‘sensory specialists’ might sustain themselves via sensory compensation, behavioural plasticity or avoidance of detrimental cues in the short term, or via genetic adaptation in the longer term. Due to the rapid loss of natural cuescapes, alternative research agendas are needed to monitor and measure multicue changes throughout the oceans. Together with mechanistic and field studies of animal responses, such research can inform management by identifying the species most at risk and the areas that may be suitable for cuescape preservation

Serum levels of interleukin-6 are not elevated in patients with Alzheimer's disease

Serum levels of interleukin-6 (IL-6) were determined in 97 patients with clinically diagnosed Alzheimer's disease and 79 age- and sex-matched control subject. Median serum levels of IL-6 did not differ significantly between Alzheimer patients (8.6 U/ml) and controls (8.2 U/ml). Median levels of serum IL-6 were similar for sporadic and familial patients. The concentration of IL-6 was not associated with the severity of the dementia or the duration of the disease since first symptoms. According to these observations there is no evidence for a significant elevation in serum IL-6 in Alzheimer's disease

Mangroves enhance the biomass of coral reef fish communities in the Caribbean

Mangrove forests are one of the world's most threatened tropical ecosystems with global loss exceeding 35% (ref. 1). Juvenile coral reef fish often inhabit mangroves, but the importance of these nurseries to reef fish population dynamics has not been quantified. Indeed, mangroves might be expected to have negligible influence on reef fish communities: juvenile fish can inhabit alternative habitats and fish populations may be regulated by other limiting factors such as larval supply or fishing. Here we show that mangroves are unexpectedly important, serving as an intermediate nursery habitat that may increase the survivorship of young fish. Mangroves in the Caribbean strongly influence the community structure of fish on neighbouring coral reefs. In addition, the biomass of several commercially important species is more than doubled when adult habitat is connected to mangroves. The largest herbivorous fish in the Atlantic, Scarus guacamaia, has a functional dependency on mangroves and has suffered local extinction after mangrove removal. Current rates of mangrove deforestation are likely to have severe deleterious consequences for the ecosystem function, fisheries productivity and resilience of reefs. Conservation efforts should protect connected corridors of mangroves, seagrass beds and coral reefs

Simple ecological trade-offs give rise to emergent cross-ecosystem distributions of a coral reef fish

Ecosystems are intricately linked by the flow of organisms across their boundaries, and such connectivity can be essential to the structure and function of the linked ecosystems. For example, many coral reef fish populations are maintained by the movement of individuals from spatially segregated juvenile habitats (i.e., nurseries, such as mangroves and seagrass beds) to areas preferred by adults. It is presumed that nursery habitats provide for faster growth (higher food availability) and/or low predation risk for juveniles, but empirical data supporting this hypothesis is surprisingly lacking for coral reef fishes. Here, we investigate potential mechanisms (growth, predation risk, and reproductive investment) that give rise to the distribution patterns of a common Caribbean reef fish species, Haemulon flavolineatum (French grunt). Adults were primarily found on coral reefs, whereas juvenile fish only occurred in non-reef habitats. Contrary to our initial expectations, analysis of length-at-age revealed that growth rates were highest on coral reefs and not within nursery habitats. Survival rates in tethering trials were 0% for small juvenile fish transplanted to coral reefs and 24–47% in the nurseries. As fish grew, survival rates on coral reefs approached those in non-reef habitats (56 vs. 77–100%, respectively). As such, predation seems to be the primary factor driving across-ecosystem distributions of this fish, and thus the primary reason why mangrove and seagrass habitats function as nursery habitat. Identifying the mechanisms that lead to such distributions is critical to develop appropriate conservation initiatives, identify essential fish habitat, and predict impacts associated with environmental change

Ocean acidification drives global reshuffling of ecological communities

First published: 29 September 2022The paradigm that climate change will alter global marine biodiversity is one of the most widely accepted. Yet, its predictions remain difficult to test because laboratory systems are inadequate at incorporating ecological complexity, and common biodiversity metrics have varying sensitivity to detect change. Here, we test for the prevalence of global responses in biodiversity and community-level change to future climate (acidification and warming) from studies at volcanic CO2 vents across four major global coastal ecosystems and studies in laboratory mesocosms. We detected globally replicable patterns of species replacements and community reshuffling under ocean acidification in major natural ecosystems, yet species diversity and other common biodiversity metrics were often insensitive to detect such community change, even under significant habitat loss. Where there was a lack of consistent patterns of biodiversity change, these were a function of similar numbers of studies observing negative versus positive species responses to climate stress. Laboratory studies showed weaker sensitivity to detect species replacements and community reshuffling in general. We conclude that common biodiversity metrics can be insensitive in revealing the anticipated effects of climate stress on biodiversity—even under significant biogenic habitat loss—and can mask widespread reshuffling of ecological communities in a future ocean. Although the influence of ocean acidification on community restructuring can be less evident than species loss, such changes can drive the dynamics of ecosystem stability or their functional change. Importantly, species identity matters, representing a substantial influence of future oceans.Ivan Nagelkerken, Sean D. Connel

Species range shifts along multistressor mosaics in estuarine environments under future climate

First published online 16 October 2019Range shifts are a key mechanism that species employ in response to climate change. Increasing global temperatures are driving species redistributions to cooler areas along three main spatial axes: increasing latitudes, altitudes and water depths. Climate‐mediated range shift theory focuses on temperature as the primary ecological driver, but global change alters other environmental factors as well, and these rarely work in isolation. Ecosystems are often characterized as mosaics of overlapping environmental stressors, resulting in temporal and spatial heterogeneity which differs between stable, low complexity mosaics (e.g. open ocean) and highly variable, highly complex mosaic environments (e.g. estuaries). We propose a multistressor mosaic of climate‐mediated species range shift across abiotic environmental gradients, typical for mobile species (e.g. fish) in variable coastal environments. We conceptualize how climate‐driven changes in salinity, temperature, dissolved oxygen and pH can drive redistribution of estuarine species in a future world. Non‐thermal drivers are a critical component of species range shifts and when not considered, underestimate the impact of global change on species populations and ecosystem services.Shannon S. Lauchlan, Ivan Nagelkerke

Global alteration of ocean ecosystem functioning due to increasing human CO(2) emissions

Rising anthropogenic CO₂ emissions are anticipated to drive change to ocean ecosystems, but a conceptualization of biological change derived from quantitative analyses is lacking. Derived from multiple ecosystems and latitudes, our metaanalysis of 632 published experiments quantified the direction and magnitude of ecological change resulting from ocean acidification and warming to conceptualize broadly based change. Primary production by temperate noncalcifying plankton increases with elevated temperature and CO₂, whereas tropical plankton decreases productivity because of acidification. Temperature increases consumption by and metabolic rates of herbivores, but this response does not translate into greater secondary production, which instead decreases with acidification in calcifying and noncalcifying species. This effect creates a mismatch with carnivores whose metabolic and foraging costs increase with temperature. Species diversity and abundances of tropical as well as temperate species decline with acidification, with shifts favoring novel community compositions dominated by noncalcifiers and microorganisms. Both warming and acidification instigate reduced calcification in tropical and temperate reef-building species. Acidification leads to a decline in dimethylsulfide production by ocean plankton, which as a climate gas, contributes to cloud formation and maintenance of the Earth's heat budget. Analysis of responses in short- and long-term experiments and of studies at natural CO₂ vents reveals little evidence of acclimation to acidification or temperature changes, except for microbes. This conceptualization of change across whole communities and their trophic linkages forecast a reduction in diversity and abundances of various key species that underpin current functioning of marine ecosystems.Ivan Nagelkerken and Sean D. Connel