Biogeographic Transition Zone Research Articles

Past and future impacts of marine heatwaves on small-scale fisheries in Baja California, Mexico

Marine heatwaves are globally occurring events that can negatively impact fisheries, but their impacts on small-scale operations remain understudied. We investigate the historical and future impacts of marine heatwaves on small-scale fisheries operating along a biogeographic transition zone in the Baja California Peninsula, Mexico. We estimate the impacts of the most intense marine heatwave regime on record on fisheries production of 43 economic units operating in a system of 55 Territorial Use-Rights for Fisheries. During this regime, aggregate landings in the lobster, sea urchin, and sea cucumber fisheries decreased between 15 and 58%. Most operations (56%) presented large reductions in landings, whose losses more than outweigh the small increase detected for the other 44%. Notably, impacts were larger for fisheries operating near an equatorward biogeographic break, and for operations in areas of high historical environmental variation and low historical variation in fisheries production. Climate models predict an increase in the frequency and intensity of exposure to marine heatwaves for all fisheries, but the change in frequency and intensity will be greater for those in the north. In the face of extreme environmental shocks such as marine heatwaves, small-scale fisheries operating near biogeographic transition zones are among the most vulnerable.

Patterns of Zoological Diversity in Iran—A Review

Iran is a country characterized by high biodiversity and complex biogeographic patterns. Its diverse landscape and steep climatic gradients have resulted in significant faunal diversity and high level of endemism. To better understand these patterns, we investigated the historical environmental drivers that have shaped Iran’s current geological and climatological conditions, and, consequently, have shaped the current zoological distribution patterns. Furthermore, we provide an overview of the country’s zoological diversity and zoogeography by reviewing published studies on its fauna. We analyzed nearly all available catalogs, updated checklists, and relevant publications, and synthesized them to present a comprehensive overview of Iran’s biodiversity. Our review reports approximately 37,500 animal species for Iran. We also demonstrated that the country serves as a biogeographic transition zone among three zoogeographical realms: the Palearctic, Oriental, and Saharo-Arabian, where distinct faunal elements intersect. This biogeographic complexity has made it challenging to delineate clear zoogeographical zones, leading to varying classifications depending on the taxon. The uplift of mountain ranges, in particular, has played a crucial role in shaping faunal diversity by serving as barriers, corridors, and glacial refugia. These mountains are largely the result of orogeny and plate collisions during the Mesozoic and Cenozoic eras, coupled with the development of the Tethyan Sea and the uplift of several ranges during the Miocene. Despite these insights, our understanding of biodiversity distribution in Iran remains incomplete, even for some well-studied taxa, such as certain vertebrate families and arthropods. We highlight the existing gaps in knowledge regarding zoogeographical patterns and propose approaches to address these gaps, particularly concerning less-studied species and the highly diverse group of insects.

Estructura comunitaria de peces, asteroideos y equinoideos en el Farallón de San Ignacio, arrecife situado en la “brecha faunística de Sinaloa”, México

Even though there is extensive research on the rocky reefs in the Gulf of California, some areas still have scarce information, such as the Farallón de San Ignacio, which is well known for its high biodiversity and its location in the biogeographic transition zone known as the "Sinaloa gap." Due to the limited information available for this site, the present study aimed to describe the composition and structure of asteroid and echinoid fish assemblages at the Farallón de San Ignacio. For this purpose, visual surveys were conducted in November 2016 using belt transects of 25 m long by 4 m wide for fish and 25 m long by 2 m wide for invertebrates, to estimate species abundance, richness, diversity, and evenness indices, and to compare them with other rocky reefs located at the same latitude on the western coast of the Gulf of California that were visited the same year. A total of 34 species were recorded, including two asteroids and four echinoids. The most abundant species were the fish Azurina atrilobata, the starfish Phataria unifacialis, and the sea urchin Diadema mexicanum. Despite the Farallón’s isolation, the complexity of its community structure is similar to that of other islands in the Gulf of California, although there were differences in species composition due to the high abundance of herbivorous species at this site.

Taxa-dependent temporal trends in the abundance and size of sea urchins in subtropical eastern Australia.

Subtropical reefs host a dynamic mix of tropical, subtropical, and temperate species that is changing due to shifts in the abundance and distribution of species in response to ocean warming. In these transitional communities, biogeographic affinity is expected to predict changes in species composition, with projected increases of tropical species and declines in cool-affinity temperate species. Understanding population dynamics of species along biogeographic transition zones is critical, especially for habitat engineers such as sea urchins that can facilitate ecosystem shifts through grazing. We investigated the population dynamics of sea urchins on coral-associated subtropical reefs at 7 sites in eastern Australia (28.196° S to 30.95° S) over 9 years (2010-2019), a period impacted by warming and heatwaves. Specifically, we investigated the density and population size structure of taxa with temperate (Centrostephanus rodgersii, Phyllacanthus parvispinus), subtropical (Tripneustes australiae) and tropical (Diadema spp.) affinities. Counter to expectation, biogeographic affinity did not explain shifts in species abundances in this region. Although we expected the abundance of tropical species to increase at their cold range boundaries, tropical Diadema species declined across all sites. The subtropical T. australiae also showed declines, while populations of the temperate C. rodgersii were remarkably stable throughout our study period. Our results show that temporal patterns of sea urchin populations in this region cannot be predicted by bio-geographic affinity alone and contribute critical information about the population dynamics of these important herbivores along this biogeographic transition zone.

Decadal demographic shifts and size-dependent disturbance responses of corals in a subtropical warming hotspot

Long-term demographic studies at biogeographic transition zones can elucidate how body size mediates disturbance responses. Focusing on subtropical reefs in eastern Australia, we examine trends in the size-structure of corals with contrasting life-histories and zoogeographies surrounding the 2016 coral bleaching event (2010–2019) to determine their resilience and recovery capacity. We document demographic shifts, with disproportionate declines in the number of small corals and long-term persistence of larger corals. The incidence of bleaching (Pocillopora, Turbinaria) and partial mortality (Acropora, Pocillopora) increased with coral size, and bleached corals had greater risk of partial mortality. While endemic Pocillopora experienced marked declines, decadal stability of Turbinaria despite bleaching, coupled with abundance increase and bleaching resistance in Acropora indicate remarkable resilience of these taxa in the subtropics. Declines in the number of small corals and variable associations with environmental drivers indicate bottlenecks to recovery mediated by inhibitory effects of thermal extremes for Pocillopora (heat stress) and Acropora (heat and cold stress), and stimulatory effects of chlorophyll-a for Turbinaria. Although our study reveals signs of resilience, it foreshadows the vulnerability of subtropical corals to changing disturbance regimes that include marine heatwaves. Disparity in population dynamics suggest that subtropical reefs are ecologically distinct from tropical coral reefs.

Adaptation to seasonal reproduction and environment-associated factors drive temporal and spatial differentiation in northwest Atlantic herring despite gene flow.

Understanding how marine organisms adapt to local environments is crucial for predicting how populations will respond to global climate change. The genomic basis, environmental factors and evolutionary processes involved in local adaptation are however not well understood. Here we use Atlantic herring, an abundant, migratory and widely distributed marine fish with substantial genomic resources, as a model organism to evaluate local adaptation. We examined genomic variation and its correlation with environmental variables across a broad environmental gradient, for 15 spawning aggregations in Atlantic Canada and the United States. We then compared our results with available genomic data of northeast Atlantic populations. We confirmed that population structure lies in a fraction of the genome including likely adaptive genetic variants of functional importance. We discovered 10 highly differentiated genomic regions distributed across four chromosomes. Nine regions show strong association with seasonal reproduction. One region, corresponding to a known inversion on chromosome 12, underlies a latitudinal pattern discriminating populations north and south of a biogeographic transition zone on the Scotian Shelf. Genome-environment associations indicate that winter seawater temperature best correlates with the latitudinal pattern of this inversion. The variation at two so-called 'islands of divergence' related to seasonal reproduction appear to be private to the northwest Atlantic. Populations in the northwest and northeast Atlantic share variation at four of these divergent regions, simultaneously displaying significant diversity in haplotype composition at another four regions, which includes an undescribed structural variant approximately 7.7 Mb long on chromosome 8. Our results suggest that the timing and geographic location of spawning and early development may be under diverse selective pressures related to allelic fitness across environments. Our study highlights the role of genomic architecture, ancestral haplotypes and selection in maintaining adaptive divergence in species with large population sizes and presumably high gene flow.

Niche partitioning among odontocetes in a marine biogeographic transition zone of the western South Atlantic Ocean

Niche partitioning among odontocetes in a marine biogeographic transition zone of the western South Atlantic Ocean

Rapid tropicalization evidence of subtidal seaweed assemblages along a coastal transitional zone

Anthropogenic climate change, particularly seawater warming, is expected to drive quick shifts in marine species distribution transforming coastal communities. These shifts in distribution will be particularly noticeable in biogeographical transition zones. The continental Portuguese coast stretches from north to south along 900 km. Despite this short spatial scale, the strong physical gradient intensified by the Iberian upwelling creates a transition zone where seaweed species from boreal and Lusitanian-Mediterranean origin coexist. On the northern coast, kelp marine forests thrive in the cold, nutrient-rich oceanic waters. In the south, communities resemble Mediterranean-type seaweed assemblages and are dominated by turfs. Recent evidence suggests that in these coastal areas, marine intertidal species are shifting their distribution edges as a result of rising seawater temperatures. Taking advantage of previous abundance data collected in 2012 from subtidal seaweed communities, a new sampling program was carried out in the same regions in 2018 to assess recent changes. The results confirmed the latitudinal gradient in macroalgal assemblages. More importantly we found significant structural and functional changes in a short period of six years, with regional increases of abundance of warm-affinity species, small seaweeds like turfs. Species richness, diversity, and biomass increase, all accompanied by an increase of community temperature index (CTI). Our findings suggest that subtidal seaweed communities in this transitional area have undergone major changes within a few years. Evidence of “fast tropicalization” of the subtidal communities of the Portuguese coast are strong indication of the effects of anthropic climate change over coastal assemblages.

Why biogeographical transition zones matter

AbstractBiogeographical transition zones are areas of overlap, replacement or partial segregation between different biotas, which are sets of taxa sharing similar geographical distributions as a result of a common evolutionary history and ecological affinities. Transition zones occur in a few particular areas of the world where historically contingent processes have allowed different biotic elements to coexist and interact. Evolutionary or historical biogeographers have traditionally characterized transition zones by the overlap of different biotic elements. More recently, authors applying track analyses have detected transition zones by the presence of nodes or by conflicting results in cladistic biogeographic analyses. Ecological biogeographers have taken a different approach, usually applying quantitative methods, for example, species turnover indices to analyse the strength and breadth of biogeographic transition zones. Some authors consider transition zones to represent outstanding areas for analysing the principles shaping biotic assembly, whereas others have dismissed them, sometimes as artificial. Biogeographical transition zones are particularly interesting for a truly integrative biogeography, being natural laboratories where the interaction of historical and ecological processes can be analysed fruitfully, and are especially appropriate for an integrative approach, epistemologically grounded in integrative pluralism. A coherent conceptual framework to analyse transition zones, however, is still lacking.

Comparative population genetics of congeneric limpets across a biogeographic transition zone reveals common patterns of genetic structure and demographic history.

The distribution of genetic diversity is often heterogeneous in space, and it usually correlates with environmental transitions or historical processes that affect demography. The coast of Chile encompasses two biogeographic provinces and spans a broad environmental gradient together with oceanographic processes linked to coastal topography that can affect species' genetic diversity. Here, we evaluated the genetic connectivity and historical demography of four Scurria limpets, S. scurra, S. variabilis, S. ceciliana and S. araucana, between ca. 19° S and 53° S in the Chilean coast using genome-wide SNPs markers. Genetic structure varied among species which was evidenced by species-specific breaks together with two shared breaks. One of the shared breaks was located at 22-25° S and was observed in S. araucana and S. variabilis, while the second break around 31-34° S was shared by three Scurria species. Interestingly, the identified genetic breaks are also shared with other low-disperser invertebrates. Demographic histories show bottlenecks in S. scurra and S. araucana populations and recent population expansion in all species. The shared genetic breaks can be linked to oceanographic features acting as soft barriers to dispersal and also to historical climate, evidencing the utility of comparing multiple and sympatric species to understand the influence of a particular seascape on genetic diversity.

The Odonate fauna (Insecta: Odonata) of Belihuloya, southern intermediate zone of Sri Lanka: A preliminary assessment and conservation implications

Belihuloya situated in a biogeographical transition zone in south-central Sri Lanka is being threatened by land-use changes. Establishing baseline biodiversity knowledge of an indicator taxon within this lesser explored area, the present study systematically assessed its Odonate fauna in different habitat types through a transect survey supplemented with incidental observations. Further, the morphology of larvae and exuvia of some Odonates were opportunistically documented from selected water bodies. Transect survey and opportunistic observations identified 36 species of Odonates (22 dragonflies and 14 damselflies) representing ten families, with ten Sri Lankan endemics. Four species of dragonflies and eight damselflies are nationally threatened, including critically endangered Elattoneura centralis and endangered Libellago greeni . The calculated species richness (R), Shannon-Wiener diversity (H’), evenness (E) and Simpson’s diversity (1/D) values were, 3.51, 2.40, 0.85 and 7.90 for dragonflies, and 2.85, 2.36, 0.92 and 8.68 for damselflies respectively, while two groups show vertical niche segregation. Low Odonate community similarity coefficients among habitat types indicate they are complementary for conservation planning. Out of ten Odonate species for which larval stages were recorded, the larval morphology of Anax indicus and Gynacantha dravida are described for the first time in Sri Lanka. Baseline data provided here are used for evidence-based conservation recommendations. • Odonate fauna from Belihuloya, Sri Lanka includes 36 species (22 in Anisoptera and 14 in Zygoptera). • This includes 12 nationally threatened species (2 critically endangered [CR], 1 endangered [EN] and 9 vulnerable [VU]). • The larval morphology of Anax indicus and Gynacantha dravida are described for the first time in Sri Lanka.

Shield wall: Kelps are the last stand against corals in tropicalized reefs

Abstract Communities inhabiting biogeographic transition zones are shifting in composition as a result of progressive warming and heatwaves. In the marine environment, corals are expanding onto higher latitude reefs historically dominated by temperate kelp forests, initiating a shift towards warm affinity coral‐dominated states. Although these coral expansions are a global phenomenon, the mechanisms that are underpinning the expansion process remain poorly understood, which limits the projections of the rate and extent of ecosystem reconfiguration. Here, we investigated the interaction between the kelp Ecklonia radiata and the high latitude scleractinian coral Plesiastrea versipora in several of Western Australia's temperate reefs, where coral colony abundance has increased by 50% in recent years. Combining field surveys with field and laboratory experiments, we test the importance of physical (abrasion and light reduction) and chemical (allelopathic) effects of kelp canopies on coral tissue cover, photosynthetic parameters and calcification rates. In the field, kelp cover had a negative effect on coral density that was overwhelming in comparison to other dominant macroalgal taxa. Abrasion by kelp whiplash was the predominant mechanism by which kelp exerted a negative effect on P. versipora fitness, scraping up to 80% of live coenosarc from experimental colonies. In contrast, canopies had no effects on P. versipora photochemical efficiency and laboratory incubations showed that there were no allelochemical effects from kelp on P. versipora. We conclude that E. radiata inhibits P. versipora establishment and development through abrasion, and the survey data confirmed that recent climate‐driven kelp loss released corals from this effect, facilitating their expansion on high‐latitude reefs in Western Australia. This shows how competitive interactions actively shield against species expansion in biogeographic transition zones and suggests a continued decline of kelp canopies will increase the permeability of temperate reefs to warm affinity species such as scleractinian corals. Read the free Plain Language Summary for this article on the Journal blog.

The Abundance and Persistence of Temperate and Tropical Seagrasses at Their Edge-of-Range in the Western Atlantic Ocean

Species, including seagrasses, at their range limits are uniquely vulnerable to climate change. In the western Atlantic Ocean, the biogeographic transition zone between temperate and tropical ecosystems is recognized as one of several global hotspots where poleward-flowing western boundary currents are forecast to warm faster than the global average. In this region seagrass ecosystem services are primarily supplied by two species, Zostera marina, a temperate seagrass at its southern range limit and Halodule wrightii, a tropical seagrass at its northern limit. Water temperatures in the study location in Back Sound, North Carolina, USA have gradually increased the length of the stressful summer season for Z. marina (beginning after 3 consecutive days of daily mean water temperatures >23°C, ending after 3 consecutive days <25°C) from 84 days in 1962 to 156 days in 2019. The occurrence of extreme water temperatures also increased resulting in temperatures ≥30°C occurring more frequently in the last decade (2009-2019) than the previous 10 years. Biomass and aerial imagery collected periodically from 1981-2019 indicate that Z. marina biomass remained stable until 2008 but declined to 30-year low levels by 2019. Meadow area estimated from imagery collected during peak Z. marina biomass did not show a significant trend over time; however, lowest meadow area during the time series was recorded in 2019. Despite summer warming, H. wrightii biomass remained steady between 1979-2019 but did not replace Z. marina as the dominant species in the cooler months. We hypothesize that persistence of temperate Z. marina populations under stressful water temperatures is positively influenced by water clarity, life history, and meadow stability, due in part to the consistent presence of tropical H. wrightii maintaining meadow biomass and area. However, temperate species in edge-of-range tropicalized meadows, are still limited by physiological thresholds, and when these limits are exceeded, related declines in meadow biomass and area may not be fully replaced by tropical species immediately. Therefore, while tropicalization of seagrass meadows may result in greater resilience to abiotic stressors in the short-term, declines in biomass and area during the process of tropicalization may have significant impacts on meadow function.

Habitat change and its consequences on reef fish specialization in biogeographic transition zones

AbstractAimReef fishes are commonly recognized as sentinels of the ongoing tropicalization in biogeographic transition zones between temperate and tropical areas. Despite the reliance of these marine ectotherms on the benthos, the importance of benthic habitat has rarely been considered as a factor constraining fish distribution. Therefore, our study aims at examining the consequences of both temperature and benthic variations on the fish fauna and diagnosing potential sentinels of these environmental changes.LocationTaiwan, West Pacific.TaxonTeleostei (184 species).MethodsWe examined how the partitioning of habitats can influence the specialization of fish fauna along a latitudinal gradient. We diagnosed ‘specialist’ and ‘generalist’ fishes in this partitioning. For each specialist, we further evaluated whether its distribution is constrained by temperature, benthic habitat or both factors combined. The change in sea surface temperature over the last three decades was also monitored.ResultsFish fauna showed the highest specialization when tropical and subtropical partitions of habitat were considered. Fifty‐one tropical specialists, 7 subtropical specialists and 21 possible generalists were identified. Among specialists, 13 species were associated with temperature, 19 with habitat and 26 with both factors. Steady warming occurred across latitudes, but was accentuated in the winter of subtropical habitat.Main ConclusionsOur results suggested that the distribution of some specialist fishes was constrained only by temperature while the distribution of some others also depended on the availability of benthic habitats. Consequently, under global warming, the distribution of some specialists might shift in a manner that follows the movement of isotherms, while the distribution of others might also be conditioned by the poleward shifts of benthos. A temporal mismatch between the emergence of suitable thermal environments and the arrival of some specialists may exist. Therefore, the tropicalization of high‐latitude areas may be characterized by different waves of colonization.

Population genomic analyses reveal hybridization and marked differences in genetic structure of Scurria limpet sister species with parapatric distributions across the South Eastern Pacific.

The study of sister species that occur in parapatry around biogeographic transition zones can help understand the evolutionary processes that underlie the changes in species composition across biogeographic transition zones. The South Eastern Pacific (SEP) coast is a highly productive coastal system that exhibits a broad biogeographic transition zone around 30–35°S. Here, we present a comparative genome‐wide analysis of the sister species Scurria viridula and Scurria zebrina, that occur in parapatry and whose poleward and equatorward range edges intersect in the 30–35°S SEP biogeographic transition zone. We sampled 118 specimens sourced from nine sites from Tocopilla (22°S) to Chiloé (41°S) including one site where both species overlap and analyzed over 8000 biallelic single nucleotide polymorphisms. We found evidence of hybridization between these species in the contact zone and found significant but contrasting population structures for both species. Our results indicate that the genetic structure in S. viridula, which is currently expanding its range poleward, follows a simple isolation by distance model with no traces of natural selection (no evidence of outlier loci). In contrast, S. zebrina, which has its equatorward range edge at the transition zone, displayed a pronounced genetic break approximately at 32–34°S, along a region of marked environmental heterogeneity in association with a semi‐permanent coastal upwelling regime. For S. zebrina we also found 43 outlier loci associated with this genetic break, with a significant proportion of them clustering in a single linkage group. This marked difference in the presence of outlier loci between species suggests that they could be responding differently to local environmental challenges found at their overlapping geographic range edges, thus providing important new insights about genomic changes around biogeographic transition zones in sister species and the forces that shape genetic diversity in intertidal marine species.

Benthic transition zones in the Atlantic gateway to a changing Arctic ocean

The biogeographic transition from boreal to Arctic marine communities entails a strong taxonomic and functional turnover. Communities living in these areas are being strongly affected by climate warming with rapid reorganizations and change in ecosystem functioning. We assess the megabenthic species composition and functional character in a transition zone around Svalbard. The relationships between environment, taxonomic composition and functional traits are investigated and discussed regarding the potential impacts of climate warming. The biomass data from 293 taxa, coded with 6 functional traits (29 modalities), from 144 trawl stations, were analyzed by multivariate statistics based on taxonomy, RLQ- and fourth corner analysis, based on environment and traits. We find that boundaries between water masses and depths are associated gradual taxonomic and sharp functional transitions. We document a biogeographic transition zone on the slope northeast of Svalbard where surface deposit feeding crustacean associations meet crawling Arctic echinoderm predators. Further we show a sharp transition at 500 m depth along the shelf of Svalbard where boreal filtrating deep-sea sponges meet a unique upraised large-bodied assemblage of bathyal species on the Yermak Plateau. Global warming will likely cause rapid taxonomic and functional shifts in these transition areas, with filtrating sponges and deposit feeding crustaceans possibly expanding into Arctic communities while large, upright, predators further down the slope. There is a need for both monitoring of the transition areas, and for protecting the most vulnerable deep and arctic fauna on the Yermak Plateau.

Mitonuclear genetic patterns of divergence in the marbled crab, Pachygrapsus marmoratus (Fabricius, 1787) along the Turkish seas

Biogeographical transition zones present good opportunities for studying the effect of the past ice ages on genetic structure of species because secondary contact zones of post-glacial lineages can be formed. In this study, we investigated the population genetic structure of the marbled rock crab, Pachygrapsus marmoratus along the coasts of Turkey. We genotyped 334 individuals from the Black Sea, the Turkish Straits System (TSS), the Aegean, and the Eastern Mediterranean basins. In order to reveal its evolutionary history and its population connectivity, we used mitochondrial CO1 region and five microsatellite loci. CO1 analyzes also included 610 additional samples from Genbank, which covered most of its distribution range. Both microsatellites and mtDNA showed decreased diversity in sampling sites of the TSS and the Black Sea as compared to those along the Aegean and the Levantine coasts. There is an especially strong geographical pattern in distributions of haplotypes in mtDNA, most probably as a result of genetic drift in the Black Sea and the Sea of Marmara (SoM). Microsatellite data analyses revealed two genetically distinct clusters of P. marmoratus (clusters C and M). While individuals belonging to cluster C are present in all the sampling locations, those belonging to cluster M are only detected along the Mediterranean coasts including the Aegean and the Levantine basins. These clusters shared similar haplotypes in the Mediterranean. Haplotypes of two sympatric clusters could be similar due to incomplete lineage sorting of ancestral polymorphisms. In order to retrieve the complex demographic history and to investigate evolutionary processes resulting in sympatric clusters in the Aegean Sea and the Levantine basin, mitochondrial markers with faster mutation rates than CO1 and/or SNP data will be useful.

Local adaptation of juvenile giant kelp, Macrocystis pyrifera, from their southern limit in the northern hemisphere explored using reciprocal transplantation

ABSTRACT The Pacific coast of the Baja California peninsula (Mexico) is a unique biogeographic transition zone, where many kelp species encounter their southern subtropical limits and have experienced a range contraction in the northern hemisphere. Using reciprocal transplant experiments with giant kelp populations from their southern limit and a northern temperate site on the Baja California peninsula, we hypothesized that juveniles from the southern site would grow longer, have more fronds (an individual stipe with its blades), and have higher photosynthetic efficiency (α) and blade tissue nitrogen, especially under warmer nitrate-limited field conditions experienced in their habitat. At the southern-limit transplant site, local juveniles had more fronds compared with those from the north after 90 days in field conditions (warm waters). At the northern transplant site, blade tissue nitrogen of juveniles from both populations was low after 23 days in field conditions (not significantly different during a warm water period), however, after a further 56 day cooling period and shortly after a strong upwelling event, juveniles from the southern population had greater blade tissue nitrogen concentrations than those from the north, which showed little change. Respiration and a were both greater at higher temperatures in juveniles from the southern population, and this pattern was maintained under warm water field conditions. These physiological differences in conspecific juveniles from different populations may be driven by population-level adaptation to frequently occurring thermal and nutrient stress in southern Baja California, which is the southern distribution limit for giant kelp. Further exploration of population level differences in ecophysiology should be applied to kelp forest restoration efforts as oceans warm.

The range expansion of Clibanarius erythropus to the UK suggests that other range-shifting intertidal species may not follow

The ranges of species are shifting as a consequence of anthropogenic climate change. In the marine realm biogeographic transition zones could form barriers to dispersal and inhibit range-shift, but little is known about this potential effect. The hermit crab Clibanarius erythropus appeared in the UK in 2016 with the nearest reproducing population being on the northern coast of Brittany. This raises questions of which conditions may have permitted C. erythropus to cross the English Channel (7.25°W, 49.00°N) and whether this barrier could be overcome by other intertidal species. Dispersal simulations suggest the larvae of C. erythropus arrived in 2014, originated from North Brittany, experienced a mean temperature of around 16 °C, and took longer than 20 days to be transported across the channel. The transportation of larvae from Brittany to the southwest UK appears to be rare and driven by occasional, unusual ocean currents. The English Channel may continue to prevent species with pelagic larvae that settle within 20 days, such as many species of gastropod, annelids, and macroalgae, from successfully range expanding to the UK. North Brittany was the only landmass from which it is feasible the UK population of C. erythropus could have originated. Therefore, species with long-lived pelagic larvae but without reproducing populations in North Brittany may not appear in the southwest UK until the species are established in North Brittany. The English Channel could continue to limit the ability of many intertidal species to shift their range with climate change.

Bnormal average increase in sea surface temperature may promote the first documented mortality event of a marine sponge in the Southeastern Brazil

Frequent heat waves and mass mortality events on marine biota are positively correlated to ocean warming. Although literature has indicated some species of marine sponges, and some oceanic regions, like the Brazilian Exclusive Economic Zone, may be less affected or seem to be more resilient under future scenarios of climate changes, few studies have focused on the species responses on the climate change issue along Brazilian coast. This paradigm was undone throughout 2019 after an exceptional average increase of 2 °C in the sea surface temperature (SST) and on precipitation values since 2015 at Ilha Grande Bay (IGB, SE Brazil). The combination of SST and precipitation average increase possibly favored an environmental context for the unprecedented strong population decline and mass mortality rate of the marine sponge species Desmapsamma anchorata in the austral spring. The species used to be one of the most frequent benthic species at IGB however it was only recorded in 41.7% sites (n = 12). From 162 individuals recorded at Abraãozinho along 180 m rocky shore, 83 individuals (51.2%) were healthy, 74 (45.7%) were intensively covered by cyanobacteria and locally bleached, and five (3.1%) were completely bleached or died. Desmapsamma anchorata population deterioration in a biogeographic transition zone (Rio de Janeiro state) may reflect a shift in the marine community of IGB, opening space for opportunistic species establishment and coverage increase, since IGB has a high species turnover. The three-dimensionality, the shelter for several species, the high competitive ability and the potential to indicate polluted or not polluted areas make D. anchorata a key species for IGB monitoring in a climate change scenario.