Warm Water Anomalies Research Articles

Crossing the Pacific: Genomics Reveals the Presence of Japanese Sardine (Sardinops melanosticta) in the California Current Large Marine Ecosystem.

Recent increases in frequency and intensity of warm water anomalies and marine heatwaves have led to shifts in species ranges and assemblages. Genomic tools can be instrumental in detecting such shifts. In the early stages of a project assessing population genetic structure in Pacific Sardine (Sardinops sagax), we detected the presence of Japanese Sardine (Sardinops melanosticta) along the west coast of North America for the first time. We assembled a high quality, chromosome-scale reference genome of the Pacific Sardine and generated low coverage, whole genome sequence (lcWGS) data for 345 sardine collected in the California Current Large Marine Ecosystem (CCLME) in 2021 and 2022. Fifty individuals sampled in 2022 were identified as Japanese Sardine based on strong differentiation observed in lcWGS SNP and full mitogenome data. Although we detected a single case of mitochondrial introgression, we did not observe evidence for recent hybridization events. These findings change our understanding of Sardinops spp. distribution and dispersal in the Pacific and highlight the importance of long-term monitoring programs.

Using a deep neural network to classify echolocation clicks and identify biogeographic patterns of Pacific white-sided dolphins

Pacific white-sided dolphins are endemic to the Pacific Ocean; and two genetically distinct populations overlap along the west coast of North America. However, they are visually indistinguishable and the degree of spatial overlap remains unknown. Here, we use a deep neural network to show that the populations are acoustically distinguishable. Previous studies described two distinct echolocation click types associated with pacific white-sided dolphins and hypothesized that they were population-specific. Our neural network was trained to classify the click types based on spectral and temporal properties described previously. The neural network enabled us to analyze passive acoustic recordings from sites between the Gulf of California and the Gulf of Alaska over multiple years to investigate possible population-specific trends. The latitudinal occurrence pattern of the two click types supports the population-specific hypothesis: type A clicks continue to associate with the northern population distribution, and type B clicks with the southern population distribution. At long-term monitoring sites in Southern California, type B clicks were dominant during periods of warm water anomalies. This pattern may be an early indicator of future biogeographic shifts in the distribution of pacific white-sided dolphins and demonstrates the utility of long-term passive acoustic monitoring.

Seafloor warm water temperature anomalies impact benthic macrofauna communities of a high-Arctic cold-water fjord

Amid the alarming atmospheric and oceanic warming rates taking place in the Arctic, western fjords around the Svalbard archipelago are experiencing an increased frequency of warm water intrusions in recent decades, causing ecological shifts in their ecosystems. However, hardly anything is known about their potential impacts on the until recently considered stable and colder northern fjords. We analyzed macrobenthic fauna from four locations in Rijpfjorden (a high-Arctic fjord in the north of Svalbard) along its axis, sampled intermittently in the years 2003, 2007, 2010, 2013 and 2017. After a strong seafloor warm water temperature anomaly (SfWWTA) in 2006, the abundance of individuals and species richness dropped significantly across the entire fjord in 2007, together with diversity declines at the outer parts (reflected in Shannon index drops) and increases in beta diversity between inner and outer parts of the fjord. After a period of three years with stable water temperatures and higher sea-ice cover, communities recovered through recolonization processes by 2010, leading to homogenization in community composition across the fjord and less beta diversity. For the last two periods (2010-2013 and 2013-2017), beta diversity between the inner and outer parts gradually increased again, and both the inner and outer sites started to re-assemble in different directions. A few taxa began to dominate the fjord from 2010 onwards at the outer parts, translating into evenness and diversity drops. The inner basin, however, although experiencing strong shifts in abundances, was partially protected by a fjordic sill from impacts of these temperature anomalies and remained comparatively more stable regarding community diversity after the disturbance event. Our results indicate that although shifts in abundances were behind important spatio-temporal community fluctuations, beta diversity variations were also driven by the occurrence-based macrofauna data, suggesting an important role of rare taxa. This is the first multidecadal time series of soft-bottom macrobenthic communities for a high-Arctic fjord, indicating that potential periodic marine heatwaves might drive shifts in community structure, either through direct effects from thermal stress on the communities or through changes in environmental regimes led by temperature fluctuations (i.e. sea ice cover and glacial runoff, which could lead to shifts in primary production and food supply to the benthos). Although high-Arctic macrobenthic communities might be resilient to some extent, sustained warm water anomalies could lead to permanent changes in cold-water fjordic benthic systems.

Larval rockfish growth and survival in response to anomalous ocean conditions

Understanding how future ocean conditions will affect populations of marine species is integral to predicting how climate change will impact both ecosystem function and fisheries management. Fish population dynamics are driven by variable survival of the early life stages, which are highly sensitive to environmental conditions. As global warming generates extreme ocean conditions (i.e., marine heatwaves) we can gain insight into how larval fish growth and mortality will change in warmer conditions. The California Current Large Marine Ecosystem experienced anomalous ocean warming from 2014 to 2016, creating novel conditions. We examined the otolith microstructure of juveniles of the economically and ecologically important black rockfish (Sebastes melanops) collected from 2013 to 2019 to quantify the implications of changing ocean conditions on early growth and survival. Our results demonstrated that fish growth and development were positively related to temperature, but survival to settlement was not directly related to ocean conditions. Instead, settlement had a dome-shaped relationship with growth, suggesting an optimal growth window. Our results demonstrated that the dramatic change in water temperature caused by such extreme warm water anomalies increased black rockfish growth in the larval stage; however, without sufficient prey or with high predator abundance these extreme conditions contributed to reduced survival.

Macrobenthic diversity response to the atlantification of the Arctic Ocean (Fram Strait, 79°N) – A taxonomic and functional trait approach

This is the first study presenting temporal changes of the macrofauna biodiversity along the bathymetric gradient from the shelf to abyssal depths in the eastern Fram Striat. In this region, between 2004 and 2008, a significant increase in surface water temperature was observed due to the transport of Atlantic water from lower latitudes and was defined as a Warm Water Anomaly (WWA). Effects of the WWA in the eastern Fram Strait were observed across the entire food web, from the pelagic to the deep seafloor. The material for our study was collected before (in 2000) and after the WWA (in 2010 and 2017) at station depths ranging from 203 m to 5561 m. Samples of macrofauna and surface sediments were collected with use of a box corer to analyze species composition and functional traits, and environmental characteristics in sediments. We explore the influence of environmental changes on the structure (species composition and diversity) and functioning (functional trait composition and diversity) of macrofauna communities. An increase of primary production in surface waters during and after the WWA was reflected in a higher food availability at the seafloor from shelf to abyssal depths. Warming induced environmental changes led to an increase of macrofauna density and taxonomic diversity at all water depths. Macrofauna species composition significantly changed after the WWA. At all study sites, macrofauna functional diversity increased after the warm period. Functional trait composition changed significantly along the bathymetric transect. Despite changes in the taxonomic composition, macrofauna communities at the shallowest stations showed high functional redundancy, i.e., trait composition remained unchanged after the WWA. At water depths below 1500 m, where functional redundancy was significantly lower, functional trait composition changed significantly after the WWA. Our results suggest that macrofauna communities on the shelves are more resistant to environmental changes compared to deep-sea assemblages in the eastern Fram Strait.

Marine Heatwaves Offshore Central and South Chile: Understanding Forcing Mechanisms During the Years 2016-2017

Marine heatwaves (MHWs) are discrete warm-water anomalies events occurring in both open ocean and coastal areas. These phenomena have drawn researchers’ attention since the beginning of the 2010s, as their frequency and intensity are severely increasing due to global warming. Their impacts on the oceans are wide, affecting the ecosystems thus having repercussions on the economy by decreasing fisheries and aquaculture production. Chilean Patagonia (41° S-56° S) is characterised by fjord ecosystems already experiencing the global change effects in the form of large-scale and local modifications. This study aimed to realise a global assessment of the MHWs that have occurred along Central and South Chile between 1982 and 2020. We found that the frequency of MHWs was particularly high during the last decade offshore Northern Patagonia and that the duration of the events is increasing. During austral winter and spring 2016, combination of advected warm waters coming from the extratropical South Pacific Ocean and persisting high pressure inducing reduced winds have together diminished the heat transfer from the ocean to the atmosphere, creating optimal condition for a long-lasting MHW. That MHW hit Patagonia during 5 months, from May to October 2016, and was the longest MHW recorded over the 1982-2020 period. In addition, a global context of positive phases of El Niño Southern Oscillation and Southern Annular Mode contributed to the MHW formation.

Disturbance and distribution gradients influence resource availability and feeding behaviours in corallivore fishes following a warm-water anomaly

Understanding interactions between spatial gradients in disturbances, species distributions and species’ resilience mechanisms is critical to identifying processes that mediate environmental change. On coral reefs, a global expansion of coral bleaching is likely to drive spatiotemporal pulses in resource quality for obligate coral associates. Using technical diving and statistical modelling we evaluated how depth gradients in coral distribution, coral bleaching, and competitor density interact with the quality, preference and use of coral resources by corallivore fishes immediately following a warm-water anomaly. Bleaching responses varied among coral genera and depths but attenuated substantially between 3 and 47 m for key prey genera (Acropora and Pocillopora). While total coral cover declined with depth, the cover of pigmented corals increased slightly. The abundances of three focal obligate-corallivore butterflyfish species also decreased with depth and were not related to spatial patterns in coral bleaching. Overall, all species selectively foraged on pigmented corals. However, the most abundant species avoided feeding on bleached corals more successfully in deeper waters, where bleaching prevalence and conspecific densities were lower. These results suggest that, as coral bleaching increases, energy trade-offs related to distributions and resource acquisition will vary with depth for some coral-associated species.

Heatwave-induced synchrony within forage fish portfolio disrupts energy flow to top pelagic predators.

During the Pacific marine heatwave of 2014–2016, abundance and quality of several key forage fish species in the Gulf of Alaska were simultaneously reduced throughout the system. Capelin (Mallotus catervarius), sand lance (Ammodytes personatus), and herring (Clupea pallasii) populations were at historically low levels, and within this community abrupt declines in portfolio effects identify trophic instability at the onset of the heatwave. Although compensatory changes in age structure, size, growth or energy content of forage fish were observed to varying degrees among all these forage fish, none were able to fully mitigate adverse impacts of the heatwave, which likely included both top‐down and bottom‐up forcing. Notably, changes to the demographic structure of forage fish suggested size‐selective removals typical of top‐down regulation. At the same time, changes in zooplankton communities may have driven bottom‐up regulation as copepod community structure shifted toward smaller, warm water species, and euphausiid biomass was reduced owing to the loss of cold‐water species. Mediated by these impacts on the forage fish community, an unprecedented disruption of the normal pelagic food web was signaled by higher trophic level disruptions during 2015–2016, when seabirds, marine mammals, and groundfish experienced shifts in distribution, mass mortalities, and reproductive failures. Unlike decadal‐scale variability underlying ecosystem regime shifts, the heatwave appeared to temporarily overwhelm the ability of the forage fish community to buffer against changes imposed by warm water anomalies, thereby eliminating any ecological advantages that may have accrued from having a suite of coexisting forage species with differing life‐history compensations.

Three-dimensional cross-shelf zooplankton distributions off the Central Oregon Coast during anomalous oceanographic conditions

The Northern California Current (NCC) is a complex, dynamic system experiencing distinctly different levels of upwelling and downwelling, ranging from intermittent upwelling in summer to downwelling in winter. In recent years, warm water anomalies along the Oregon coast have had significant effects on coastal plankton assemblages. To resolve some of the fine-scale responses to these conditions, we used a towed, undulating underwater imaging system to investigate fine-scale (1 m vertical) zoo- and ichthyoplankton distributions along a 57-km section parallel to the Newport Hydrographic Line encompassing the shelf, shelf break, and slope off the central coast of Oregon. A sparse Convolutional Neural Network was used to automate the identification of 52 million plankton images of 64 plankton taxa, ranging from protists to copepods, larval fishes, and gelatinous organisms. Taxa distributions were interpolated over the whole transect, providing unprecedented insight into their horizontal and vertical distributions and revealing seven broad patterns of distribution. Additional fine-scale distribution data enable examination of some of the physical and biological processes underlying these fine-scale distribution patterns, building upon the historical time series data that exists for this region and advancing our knowledge of planktonic processes in this productive region of the NCC.

Ecological implications of unprecedented warm water anomalies on interannual prey preferences and foraging areas of Guadalupe fur seals

AbstractThe Guadalupe fur seal (GFS) currently is recovering from near extinction and prey availability is an important factor. Scat and stable isotope analyses (SIA) were used to assess GFS foraging on Guadalupe Island during 2013–2016. This period was characterized by normal (2013) ocean temperatures followed by warm conditions (2014–2016). Scat samples (~40/year) were collected for prey identification. Additionally, lanugo samples from 1‐month‐old pups (50/year) were processed for SIA (δ13C/δ15N). Interannual prey preferences were identified (ANOSIM,p < .05), including significant differences between 2013 and the anomalous years. The most important prey species among these years was the jumbo squid; followed by the neon flying squid (2014–2016). The GFS diet was more specialized in 2013–2015 and more generalized in 2016. Prey from higher trophic levels (determined by scat analysis) were consumed during 2014–2016, but with significantly lower δ13C/δ15N values than in 2013 (ANOVA,p < .05 for both isotope ratios). This pattern may indicate more northerly or offshore foraging areas, with the presence of oceanic prey (neon flying squid). The widest isotopic niche was observed in 2015 (2.2‰2), reflecting a broader foraging area. Our findings are an important step toward better understanding the impacts of climate change on the recovery of GFS.

Coral community life histories and population dynamics driven by seascape bathymetry and temperature variability.

Temperature variability, habitat, coral communities, and fishing intensity are important factors influencing coral responses to climate change. Consequently, chronic and acute sea-surface temperatures (SSTs) and their interactions with habitat and fishing were studied along the East African coast (~400km) by evaluating changes over a ~25-year period in two major reef habitats-island and fringing reefs. These habitats had similar mean and standard deviation temperature measurements but differed in that islands had lower ocean heights and flatter and less right-skewed temperature distributions than fringing reefs. These patterns arise because islands are exposed to deep offshore water passing through deep channels while being protected from the open ocean storms and the strong inter-annual current temperature variability. Within these two seascapes, coral communities are shaped by population responses to the variable temperature distributions as determined by the taxa's associations with the competitive-stress-ruderal (CSR) life history groups. For example, competitive taxa were more abundant where temperature distributions were flat and lacked frequent warm water anomalies. In contrast, ruderal, weedy, and generalist taxa were more common where temperature distributions were centralized, standard deviations high, and warm water anomalies more frequent. Finally, stress-resistant taxa were more common in reefs with high temperature skew but flatter temperature distributions. The rare 1998 thermal anomaly impacted and disturbed the ruderal and stressed reef more than the competitive communities. Ruderal became more similar to stressed communities while the stressed community moved further from the mean before recovering towards the competitive community. Competitive taxa were more common on islands and the deeper fringing reef sites while ruderal were dominant in shallow fringing reef lagoons. Over time, islands were less disturbed than fringing reefs and maintained the highest coral cover, numbers of taxa, and most competitive or space-occupying taxa. However, some island reefs with a history of dynamite fishing aligned with the stress-resistant communities over the full study period. Compared to the in situ SST gauges at the study site, temperature proxies with global coverage were often good at estimating mean and standard deviations of the SSTs but much poorer at estimating the shape of the temperature distributions that reflect chronic and acute stress, as reflected by kurtosis and skewness metrics. Given that these stress variables were critical for understanding the impacts of rare climate disturbances, global climate models that use mean conditions are likely to be poor predictors of future impacts on corals, particularly their species and life history composition. Better predictions should be possible if appropriate chronic and acute stress metrics and their proxies are identified and used.

Algal toxins in Alaskan seabirds: Evaluating the role of saxitoxin and domoic acid in a large-scale die-off of Common Murres

Elevated seawater temperatures are linked to the development of harmful algal blooms (HABs), which pose a growing threat to marine birds and other wildlife. During late 2015 and early 2016, a massive die-off of Common Murres (Uria aalge; hereafter, murres) was observed in the Gulf of Alaska coincident with a strong marine heat wave. Previous studies have documented illness and death among seabirds resulting from exposure to the HAB neurotoxins saxitoxin (STX) and domoic acid (DA). Given the unusual mortality event, corresponding warm water anomalies, and recent detection of STX and DA throughout coastal Alaskan waters, HABs were identified as a possible factor of concern. To evaluate whether algal toxins may have contributed to murre deaths, we tested for STX and DA in a suite of tissues obtained from beach-cast murre carcasses associated with the die-off as well as from apparently healthy murres and Black-legged Kittiwakes (Rissa tridactyla; hereafter, kittiwakes) sampled in the preceding and following summers. We also tested forage fish and marine invertebrates collected in the Gulf of Alaska in 2015–2017 to evaluate potential sources of HAB toxin exposure for seabirds. Saxitoxin was present in multiple tissue types of both die-off (36.4 %) and healthy (41.7 %) murres and healthy kittiwakes (54.2 %). Among birds, we detected the highest concentrations of STX in liver tissues (range 1.4–10.8 μg 100 g−1) of die-off murres. Saxitoxin was relatively common in forage fish (20.3 %) and invertebrates (53.8 %). No established toxicity limits currently exist for seabirds, but concentrations of STX in birds and forage fish in our study were lower than values reported from most other bird die-offs in which STX intoxication was causally linked. We detected low concentrations of DA in a single bird sample and in 33.3 % of invertebrates and 4.0 % of forage fish samples. Although these results do not support the hypothesis that acute exposure to STX or DA was a primary factor in the 2015–2016 mortality event, additional information about the sensitivity of murres to these toxins is needed before we can discount their potential role in the die-off. The widespread occurrence of STX in seabirds, forage fish, and invertebrates in the Gulf of Alaska indicates that algal toxins should be considered in future assessments of seabird health, especially given the potential for greater occurrence of HABs in the future.

Regional Structure in the Marine Heat Wave of Summer 2015 Off the Western United States

One of the largest warm water anomalies (marine heat waves [MHWs]) ever recorded occurred in the northeast Pacific during 2014--2016. This MHW was caused by large-scale atmospheric ridging and affected fisheries and ecosystems from Alaska through California, including a bloom of toxic algae spanning the entire coastline. Regional variations in MHW severity are common along coastlines worldwide but are generally unexplained. During the 2014--16 MHW, the summertime sea-surface temperature (SST) anomalies were often stronger along the southern half of the coastline off the western continental United States. The reason for this north-south difference in severity of the MHW within the California Current System (CCS) has remained unclear. The scientific community's lack of understanding of regional variations within MHWs prevents accurate prediction of SST anomalies and resulting ecological and economic impacts. We show the north-south difference in SST anomalies was due to a known wind pattern determined by the coastline shape. The wind anomalies in summer have a quasi-dipole structure: the northern lobe extends southwest from Washington/Oregon, and the southern lobe has opposite sign and extends south from Cape Mendocino in a triangle due to a hydraulic expansion fan in the marine boundary layer. The alternating wind intensifications and relaxations typically last several days. However, the large-scale ridging during the MHW was associated with unusual persistence in this pattern: in summer 2015 a single wind relaxation in the southern lobe lasted two weeks. These wind anomalies induce changes in SST, likely via changes in wind-driven vertical entrainment of cold water from below the mixed layer, and mixed-layer shoaling; the net air-sea heat flux anomaly is small. The July 2015 wind relaxation persisted so long that the changes in SST exceeded pre-existing SST variations. The resulting SST anomalies have a dipole pattern similar to the wind anomalies. These dipole SST anomalies explain the north-south asymmetry in the CCS MHW. We suggest that during future persistent ridging events, the SST anomalies off the western continental U.S. will develop a north-south split structure similar to July 2015.

Shifts in the distribution and abundance of coastal marine species along the eastern Pacific Ocean during marine heatwaves from 2013 to 2018

BackgroundOngoing global ocean warming and a recent increase in the frequency and duration of marine heatwaves have demonstrably impacted marine ecosystems. Growing evidence points to both short- and long-term biological changes, across several levels of organization. While range shifts are among the predicted responses, few studies are focused solely on documenting such changes. Here we report ecological changes in response to marine heatwaves across multiple taxa in the eastern Pacific from central California to Baja California.MethodsSea surface temperature data from two estuaries and one coastal site were analyzed to define the number, duration, and intensity of marine heatwaves occurring in central and southern California from 2013 to 2018. Long-term monitoring programs and short-term research projects in coastal and estuarine ecosystems serendipitously collected specimens or photographs of extralimital species from central California to the Baja California Peninsula. Spatial and temporal sampling protocols and the targeted species for six unrelated programs varied greatly, from annual to monthly at both fixed and variable locations. In addition, anomalous occurrences were reported to staff at local and regional marine and estuarine protected areas and noted in local news and social media outlets. Anomalous range detections were categorized as range expansions and extensions, reappearances, abundance increases, shifts into new habitats, and range contractions.ResultsMultiple marine heatwaves occurred from 2014 to 2018, peaking in 2015. Marine heatwaves were more intense and longer in the estuaries, with a maximum duration of 109 days in 2015. We observed 29 species that had responded to the warm water anomalies of 2014–2018 along the eastern Pacific Ocean between central California and the Baja California Peninsula: 7 expansions, 2 extensions, 10 reappearances, 7 increases, 2 shifts into new habitats, and 1 apparent contraction. These shifts included algae, invertebrates and fishes. Twenty species were observed by professional biologists involved both in long-term monitoring programs and short-term studies, 6 by amateur naturalists as part of community-based science programs in the field, and 3 through a combination of all three.ConclusionsIncreased warm waters, sustained for an unprecedented 4 of 5 years, facilitated the northward redistribution of multiple species from several taxonomic groups. Species shifting northward were from warm-temperate and subtropical ecosystems to the south. In the absence of programs designed to detect range shifts, we must rely on the serendipitous observations of biologists conducting both long-term monitoring and short-term research, and the growing wealth of information from community-based science programs made available via online databases.

Pacific modulation of accelerated south Indian Ocean sea level rise during the early 21st Century

The south Indian Ocean has shown an unprecedented sea-level rise during the early 21st Century. Sea-level rise in the south Indian Ocean is found to be 37% quicker than the global mean sea-level during 2000–2015. Observational datasets and long-term proxy records identify Pacific origin of the south Indian Ocean sea-level rise. Our results indicate that co-evolution of the cold phase of Pacific decadal oscillation (PDO) and prolonged La Nina-like condition enhances the equatorial Pacific easterlies. Stronger in-phase association of these major Pacific climate modes and equatorial Pacific easterlies enhances the Indonesian throughflow (ITF), transporting fresh and warm water anomalies from western tropical Pacific into the south Indian Ocean. As a result, south Indian Ocean sea-level rise has accelerated more than the global, with 40% contribution from the halosteric sea level primarily through the ITF transport and a secondary from the local processes during 2000–2015. The co-evolution of PDO and the south Indian Ocean sea level is also evident from the long-term proxy records indicating that the association is part of an internal mode of variability modulated on decadal time-scales. The finding from the study cautions that accelerated heat and freshwater intrusion from the western Pacific with the co-evolution of PDO and La Nina-like condition may lead to the accelerated sea-level rise and marine heat waves in the south Indian Ocean imposing threats to the life of coral reefs and marine ecosystems.

Depth-dependent temperature variability in the Southern California bight with implications for the cold-water gorgonian octocoral Adelogorgia phyllosclera

Cold-water corals are highly sensitive to changes in water temperature, as it is an important determinant of their distribution. In recent years, several heatwave events have occurred in multiple marine ecosystems, including the northeast Pacific Ocean. However, the effects of elevated ocean temperatures on cold-water corals are largely unknown. Determining the upper thermal limits of cold-water octocorals is an important first step in identifying if warm-water events pose a potential threat. Temperature data were obtained from loggers placed in the Channel Islands National Marine Sanctuary (CINMS) at 20, 50, 100, and 200 m prior to the 2015–2016 El Niño Southern Oscillation (ENSO) event and used to characterize warm-water anomalies. Live colonies of the common gorgonian octocoral, Adelogorgia phyllosclera, were collected from the CINMS using a remotely operated vehicle (ROV) and transported to laboratory aquaria where they were maintained. A laboratory study was conducted to investigate the upper thermal limit of A. phyllosclera during a series of temperature assays using coenenchyme health scores, polyp activity, and estimated survival. Results of in-situ temperature analyses indicated that warm-water anomalies occurred frequently at 50 and 100 m, with most of these anomalies occurring during strong ENSO months. Based on the laboratory temperature assays, the upper thermal limit of A. phyllosclera was estimated to be 20 °C, with a time to effect of 96 hours. During the 2015–2016 ENSO event, this upper thermal limit was exceeded (21.1 °C) by warm-water anomalies at 20 m that lasted up to 14.1 hours, and approached (18.3 °C) by warm-water anomalies at 50 m that lasted up to 52.7 hours. Projections for future warm-water events suggest that the upper thermal limit of A. phyllosclera and other cold-water corals will likely be reached more frequently in the coming years. Thus, understanding the responses of cold-water corals to thermal stress will help predict the resilience of these species to future ocean warming.

Rain, Runoff, and Diatoms: the Effects of the North Pacific 2014\u20132015 Warm Anomaly on Particle Flux in a Canadian West Coast Fjord

Sediment traps were deployed at 50 m depth in Douglas Channel, a fjord on the west coast of Canada, for 3 years (July 2013–July 2016). Particle flux was related to rain, freshwater discharge, and phytoplankton blooms. The North Pacific warm water anomaly (known popularly as the Blob) reached coastal waters during the second year of deployment, resulting in more autumn rain and less snow than during the other 2 years. The maximum particle flux was associated with the snowfed river freshet in May during the first year and with heavy October rains during the second and third years. A protracted sedimentation event consisting of copious diatoms occurred during the warm, second winter (December 2014–February 2015). Silica (empty diatom frustules) was exported, intercepting silicate from local rivers that might otherwise have reached the outer shelf. The effects of extreme climate events are experienced differently inshore than offshore, because they are mediated by local hydrology. During the Blob year, Douglas Channel experienced exceptionally high rainfall in October, which resulted in high particle flux. As the climate continues to warm, mild, rainy years like 2014–2015 will become more common, with the possibility of further winter blooms.

Constrained nearshore larval distributions and thermal stratification

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 595:105-122 (2018) - DOI: https://doi.org/10.3354/meps12561 Constrained nearshore larval distributions and thermal stratification Malloree L. Hagerty1,*, Nathalie Reyns1, Jesús Pineda2 1Environmental and Ocean Sciences Department, University of San Diego, San Diego, California 92110, USA 2Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA *Corresponding author: mhagerty@sandiego.edu ABSTRACT: Vertical and cross-shore distributions and abundances of shallow-water barnacle larvae were characterized in La Jolla, southern California (USA), during a 2 yr period. Five stations located within 1 km of shore and ranging from 4-12 m water depths were sampled intensively in 2 m depth intervals during 27 cruises throughout spring-summer (April-July) and fall-winter (October-December) of 2014 and 2015. Larval abundances significantly decreased from 2014 to 2015, which could be related to the arrival of a warm-water anomaly (the so-called ‘Blob’) in 2014 and El Niño conditions in 2015. Despite the presence of these large-scale regional disturbances, vertical and cross-shore larval distributions were consistent throughout the 2 yr study period. Early-stage nauplii and Chthamalus fissus cyprids tracked bottom depth, and cyprids were on average deeper than nauplii. Vertical distributions were not related to the mid-depth of the thermocline or thermal stratification. Early-stage nauplii had a broader cross-shore distribution than cyprids, which were concentrated at inshore stations. Nearshore cyprid concentration had a positive relationship with thermal stratification, and the center of distribution of cyprids was farther offshore during fall-winter when stratification decreased. These results suggest that thermal stratification elicits enhanced behavioral control of cyprids to remain close to shore and reach the adult habitat. KEY WORDS: Barnacle larvae · Chthamalus fissus · Early-stage nauplii · Cyprids · Hydrographic and hydrodynamic conditions Full text in pdf format Corrigendum PreviousNextCite this article as: Hagerty ML, Reyns N, Pineda J (2018) Constrained nearshore larval distributions and thermal stratification. Mar Ecol Prog Ser 595:105-122. https://doi.org/10.3354/meps12561 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 595. Online publication date: May 14, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Single-Cell Biomolecular Analysis of Coral Algal Symbionts Reveals Opposing Metabolic Responses to Heat Stress and Expulsion

The success of corals in nutrient poor environments is largely attributed to the symbiosis between the cnidarian host and its intracellular alga. Warm water anomalies have been shown to destabilise this symbiosis, yet detailed analysis of the effect of temperature and expulsion on cell-specific carbon and nutrient allocation in the symbiont is limited. Here, we exposed colonies of the hard coral Acropora millepora to heat stress and using synchrotron-based infrared microscpectroscopy measured the biomolecular profiles of individual in hospite and expelled symbiont cells at an acute state of bleaching. Our results showed symbiont metabolic profiles to be remarkably distinct with heat stress and expulsion, where the two effectors elicited opposing metabolic adjustments independent of treatment or cell type. Elevated temperature resulted in biomolecular changes reflecting cellular stress, with relative increases in free amino acids and phosphorylation of molecules and a concomitant decline in protein content, suggesting protein modification and degradation. This contrasted with the metabolic profiles of expelled symbionts, which showed relative decreases in free amino acids and phosphorylated molecules, but increases in proteins and lipids, suggesting expulsion lessens the overall effect of heat stress on the metabolic signature of the algal symbionts. Interestingly, the combined effects of expulsion and thermal stress were additive, reducing the overall shifts in all biomolecules, with the notable exception of the significant accumulation of lipids and saturated fatty acids. This first use of a single-cell metabolomics approach on the coral symbiosis provides novel insight into coral bleaching and emphasises the importance of a single-cell approach to demark the cell-to-cell variability in the physiology of coral cellular populations.

Models of Plankton Community Changes during a Warm Water Anomaly in Arctic Waters Show Altered Trophic Pathways with Minimal Changes in Carbon Export

Carbon flow through pelagic food webs is an expression of the composition, biomass and activity of phytoplankton as primary producers. In the near future, severe environmental changes in the Arctic Ocean are expected to lead to modifications of phytoplankton communities. Here, we used a combination of linear inverse modeling and ecological network analysis to study changes in food webs before, during, and after an anomalous warm water event in the eastern Fram Strait of the West Spitsbergen Current (WSC) that resulted in a shift from diatoms to flagellates during the summer (June–July). The model predicts substantial differences in the pathways of carbon flow in diatom- vs. Phaeocystis/nanoflagellate-dominated phytoplankton communities, but relatively small differences in carbon export. The model suggests a change in the zooplankton community and activity through increasing microzooplankton abundance and the switching of meso- and macrozooplankton feeding from strict herbivory to omnivory, detritivory and coprophagy. When small cells and flagellates dominated, the phytoplankton carbon pathway through the food web was longer and the microbial loop more active. Furthermore, one step was added in the flow from phytoplankton to mesozooplankton, and phytoplankton carbon to higher trophic levels is available via detritus or microzooplankton. Model results highlight how specific changes in phytoplankton community composition, as expected in a climate change scenario, do not necessarily lead to a reduction in carbon export.