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Results for “Marine Ecologly Progressive Series”

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At least 109 records · Page 6Linked to original sources
USGS2019

Confluences function as ecological hotspots: Geomorphic and regional drivers can help identify patterns of fish distribution within a seascape

Quantifying heterogeneity in animal distributions through space and time is a precursor to addressing many important research and management issues. Obtaining these distributional data is especially difficult for mobile organisms that use broader geographic extents. Here, we asked if the merger between 2 research directions—(1) quantifying spatial linkages between fish and geomorphic features (e.g. confluences) and (2) analyzing larger-scale, multi-metric organismal patterns—can provide a broader geographic context for ecological issues that depend on understanding dynamic fish distribution. To address these objectives, we collected data from 59 tagged striped bass Morone saxatilis that were detected by a 26 acoustic receiver array deployed within Plum Island Estuary, MA, USA. We examined these telemetry data using generalized linear mixed models and chi-squared, cluster, and network analyses. Geomorphic site types informed the estuary-wide distribution of striped bass in that tagged fish spent the most time at confluence junctions; however, they did not spend the same amount of time at all junctions. Relative to integrating multiple metrics, number of tagged fish, residence time, and number of movements were not the same across all receivers. When all 3 metrics were considered together, 4 distinct clusters of distributional patterns emerged. Network analyses connected geomorphology and multi-metric seascape patterns. Confluence junctions in the Rowley and Middle regions were the most connected (high centrality) and most used sites (high residence time). Although confluence junctions function as ecological hotspots, researchers and managers will benefit from interpreting geomorphology within a larger geographic context.

Massachusetts↗
USGS2020

Combined influence of intrinsic and environmental factors in shaping productivity in a small pelagic gull, the black-legged kittiwake Rissa tridactyla

While we have a good understanding in many systems of the effects of single variable changes on organisms, we understand far less about how variables act in concert to affect living systems, where interactions among variables can lead to unanticipated results. We used mixed-effect models to evaluate the effects of multiple variables that we expected to play a role in the early reproductive stages of a North Pacific seabird, the black-legged kittiwake Rissa tridactyla, during 1992-2008 using data collected on known-aged individuals. Our work revealed the potential for contrasting stressor effects across successive stages of reproduction. Bird age, timing of egg laying, and winter ENSO conditions best explained individual laying success, such that laying success was greater when parents were older, the average winter ENSO index was positive (as occurs during El Niño episodes), and the median laying date for the colony was earlier. Age and salmon run timing (a proxy for predator presence at the colony) best explained hatching success, such that hatching success was greater when parents were older and when salmon runs were early. Identifying such differential effects of multiple stressors across consecutive reproductive stages can greatly enhance our ability to interpret trends and manage populations in the face of changes currently occurring in living systems.

Marine Ecology Progress Series↗
USGS2020

Variable prey consumption leads to distinct regional differences in Chinook salmon growth during the early marine critical period

Growth during the early marine critical period is positively associated with survival and recruitment for Pacific salmon Oncorhynchus spp., so it is important to understand how certain foraging strategies may bolster growth in estuarine and marine environments. To elucidate how spatiotemporal and demographic differences in diet contribute to growth rate variability, we analyzed stomach contents in tandem with morphometric and hormonal indices of growth for subyearling Chinook salmon O. tshawytscha captured in Puget Sound, Washington, USA. Regional dietary patterns indicated that fish caught in northern Puget Sound ate insects in the estuarine and nearshore habitats, followed by decapod larvae, euphausiids, or forage fish in the offshore zone. In southern Puget Sound, fish ate insects in the estuary but were more likely to eat mysids and other crustaceans in the nearshore zone. In the marine habitats adjacent to the San Juan Islands, subyearlings ate forage fish, and their stomachs were as much as 1.4 to 3 times fuller than salmon captured in other regions. Scale-derived growth rates and insulin-like growth factor-1 levels showed distinct growth advantages for San Juan Islands fish which were strongly associated with the early adoption of piscivory. However, consumption of larger crustaceans such as mysids and euphausiids was also associated with greater relative growth regardless of where individuals were captured. These findings highlight how spatiotemporal differences in prey quantity, prey profitability, and individual foraging strategies result in variable growth rates among salmon populations. Specifically, they emphasize the role of piscivory in promoting early marine growth for out-migrating Chinook salmon.

Washington↗
USGS2020

Growth rates for immature Kemp’s ridley sea turtles from a foraging area in the northern Gulf of Mexico

Examining vital rates helps clarify how environmental characteristics, biological resources and human activities affect population growth. Carapace lengths were gathered for 241 Kemp’s ridley Lepidochelys kempii sea turtles that were marked and recaptured (n = 23) between 2011 and 2019 at a foraging location in northwest Florida, USA. There was a strong correlation between length, width and weight of captured turtles. Mean ± SD size of all captured turtles was 36.6 ± 7.6 cm. Mean recapture interval was 499 ± 475.4 d. Straight-line carapace lengths at initial capture ranged from 20.6 to 53.3 cm. Growth rates from 0.21 to 12.44 cm yr -1 (mean 3.15 ± 2.64 cm) were documented and were greatest for turtles in the 20.0-29.9 cm size class. Growth rates from northwest Florida were slower than those reported from other sites in the Gulf of Mexico. These results indicate that Kemp’s ridleys recruit from oceanic habitat into coastal bays in northwest Florida, where they remain until they reach adulthood. However, some adult-sized turtles may continue to use the nearshore habitat. A gradient in growth rates in the Gulf of Mexico may occur from faster growth in the south to slower growth in the north. Fine-scale variations in resources and environmental conditions may drive regional differences in growth rates, and research on what drives these differences is needed.

Marine Ecology Progress Series↗
USGS2021

Biological correlates of sea urchin recruitment in kelp forest and urchin barren habitats

Shifts between the alternate stable states of sea urchin barren grounds and kelp forests correspond to sea urchin density. In the Aleutian Archipelago, green sea urchins Strongylocentrotus polyacanthus are the dominant herbivores that graze kelp forests. Sea urchin recruitment is an important driver that influences sea urchin density, particularly in the absence of top-down control from a keystone predator such as the sea otter Enhydra lutris . To understand how the biological community may influence patterns of sea urchin recruitment, we compared sea urchin recruit (size ≤20 mm) densities with biomass of other benthic organisms in both barren ground and kelp forest habitats at 9 islands across the Aleutian Archipelago. Patterns of biological community structure between the 2 habitats did not explain patterns of sea urchin recruits; however, the same 10 specific taxa were found to correlate with sea urchin recruits in each habitat. Taxa that showed strong positive correlations included Codium, Constantinea, Schizymenia, and hydrozoans, while strong negative correlations were observed with Pachyarthron and Pugettia . Weak positive correlations were observed with Alcyonidium and ascidiaceans in both habitats, while weak variable relationships were detected with Polysiphonia and Corallina between habitats. The observed species-specific relationships may be due to small sea urchin displacement by larger conspecifics, larval responses to settlement cues, post-settlement survival via biogenic refugia, or potentially predation. These potential species-specific interactions were apparent, regardless of habitat, and it can be inferred that they would be preserved in the presence or absence of keystone predation.

Alaska↗
USGS2021

Regional-scale variability in the movement ecology of marine fishes revealed by an integrative acoustic tracking network

Marine fish movement plays a critical role in ecosystem functioning and is increasingly studied with acoustic telemetry. Traditionally, this research has focused on single species and small spatial scales. However, integrated tracking networks, such as the Integrated Tracking of Aquatic Animals in the Gulf of Mexico (iTAG) network, are building the capacity to monitor multiple species over larger spatial scales. We conducted a synthesis of passive acoustic monitoring data for 29 species (889 transmitters), ranging from large top predators to small consumers, monitored along the west coast of Florida, USA, over 3 yr (2016-2018). Space use was highly variable, with some groups using all monitored areas and others using only the area where they were tagged. The most extensive space use was found for Atlantic tarpon Megalops atlanticus and bull sharks Carcharhinus leucas . Individual detection patterns clustered into 4 groups, ranging from occasionally detected long-distance movers to frequently detected juvenile or adult residents. Synchronized, alongshore, long-distance movements were found for Atlantic tarpon, cobia Rachycentron canadum , and several elasmobranch species. These movements were predominantly northbound in spring and southbound in fall. Detections of top predators were highest in summer, except for nearshore Tampa Bay where the most detections occurred in fall, coinciding with large red drum Sciaenops ocellatus spawning aggregations. We discuss the future of collaborative telemetry research, including current limitations and potential solutions to maximize its impact for understanding movement ecology, conducting ecosystem monitoring, and supporting fisheries management.

Marine Ecology Progress Series↗
USGS1996

Seagrass responses to long-term light reduction by brown tide in upper Laguna Madre, Texas: Distribution and biomass patterns

A brown tide caused by a very dense bloom of an as yet undescribed species of the new class Pelagophyceae was first reported in upper Laguna Madre, Texas, USA, in June 1990 and has been there continuously through December 1995. No change in response to reduced light was evident in the distribution of the seagrass Halodule wrightii along transects sampled before the brown tide in 1988 and resampled after initiation of the brown tide in 1991 and 1992; however, in winter 1993-94 losses were documented over 2.6 km 2 of bottom and by winter 1994-95 the area of vegetation lost had more than tripled to 9.4 km 2 . Changes in biomass presaged the changes in distribution. Decreases in biomass at depths >1.4 m were evident 2 yr before bare areas were detected. Reductions in biomass were more pronounced toward the south, in keeping with a gradient of increasing light attenuation from north to south. Support of a diminishing number of new shoots by reclamation of nutrients and stored reserves from senescing shoots and rhizomes may allow H. wrightii to persist under conditions of insufficient light for periods greatly in excess of the life span of any one shoot. This postulated capability would account for the pattern of diminishing biomass over time where the seagrass persists in deeper areas and the long lag between light reduction and change in distribution where the seagrass succumbed.

Texas↗
USGS2021

Genetic analysis of red lionfish Pterois volitans from Florida, USA, leads to alternative North Atlantic introduction scenarios

The red lionfish Pterois volitans is a successful invasive predator across the western North Atlantic, Caribbean, and Gulf of Mexico. The southeast coast of Florida (USA) has been identified as the original introduction location, but genetic analyses including Florida lionfish have yet to investigate introduction scenarios. Here, we assessed the potential lionfish invasion pathways using 1795 sequences from previously published mitochondrial D-loop sequences (n = 1558) and new samples (n = 237) from 6 locations: The Bahamas, Florida Keys, northwest Florida, North Carolina, Panamá, and southeast Florida. None of the assessed Florida lionfish (n = 394) contained the H05-H09 D-loop haplotypes found in The Bahamas, North Carolina, and Bermuda (the Northern Region), indicating that Florida was not the source for these haplotypes. Assessing the mitochondrial population structure, the Florida east coast lionfish grouped with the Caribbean/Gulf of Mexico, as opposed to the Northern Region. To further explore connectivity and invasion pathways, 14 nuclear microsatellite loci were multiplexed on lionfish collected from 15 locations (n = 394). As found in other nuclear lionfish studies, the analyses identified a lack of population structure likely due to founding effects and/or inbreeding in aquaculture brood stocks. Together, the significant haplotype differences and H01-H04 haplotypes refute Florida as the sole source of red lionfish introduction. The results of this study support alternative invasion scenarios, in which Florida was colonized as a secondary introduction site or by individuals from the Northern Region. Understanding invasive species’ population boundaries and dispersal patterns informs local control efforts and management planning for future invasive species introductions.

Florida↗
USGS2021

Unexpected diversity of Endozoicomonas in deep-sea corals

ABSTRACT: The deep ocean hosts a large diversity of azooxanthellate cold-water corals whose associated microbiomes remain to be described. While the bacterial genus Endozoicomonas has been widely identified as a dominant associate of tropical and temperate corals, it has rarely been detected in deep-sea corals. Determining microbial baselines for these cold-water corals is a critical first step to understanding the ecosystem services their microbiomes contribute, while providing a benchmark against which to measure responses to environmental change or anthropogenic effects. Samples of Acanthogorgia aspera , A. spissa , Desmophyllum dianthus , and D. pertusum ( Lophelia pertusa ) were collected from western Atlantic sites off the US east coast and from the northeastern Gulf of Mexico. Microbiomes were characterized by 16S rRNA gene amplicon surveys. Although D. dianthus and D. pertusum have recently been combined into a single genus due to their genetic similarity, their microbiomes were significantly different. The Acanthogorgia spp. were collected from submarine canyons in different regions, but their microbiomes were extremely similar and dominated by Endozoicomonas . This is the first report of coral microbiomes dominated by Endozoicomonas occurring below 1000 m, at temperatures near 4°C. D. pertusum from 2 Atlantic sites were also dominated by distinct Endozoicomonas , unlike D. pertusum from other sites described in previous studies, including the Gulf of Mexico, the Mediterranean Sea and a Norwegian fjord.

Marine Ecology Progress Series↗
USGS2021

Characterization of the biological, physical, and chemical properties of a toxic thin layer in a temperate marine system

The distribution of plankton in the ocean is patchy across a wide range of spatial and temporal scales. One type of oceanographic feature that exemplifies this patchiness is a ‘thin layer’. Thin layers are subsurface aggregations of plankton that range in vertical thickness from centimeters to a few meters, which may extend horizontally for kilometers and persist for days. We undertook a field campaign to characterize the biological, physical, and chemical properties of thin layers in Monterey Bay, California (USA), an area where these features can be persistent. The particle aggregates (marine snow) sampled in the study had several quantifiable properties indicating how the layer was formed and how its structure was maintained. Particles were more elongated above the layer, and then changed orientation angle and increased in size within the layer, suggesting passive accumulation of particles along a physical gradient. The shift in particle aggregate orientation angle near the pycnocline suggests that shear may also have played a role in generating the thin layer. Pseudo-nitzschia spp. were the most abundant phytoplankton within the thin layer. Further, both dissolved and particulate domoic acid were highest within the thin layer. We suggest that phosphate stress is responsible for the formation of Pseudo-nitzschia spp. aggregates. This stress together with increased nitrogen in the layer may lead to increased bloom toxicity in the subsurface blooms of Pseudo-nitzschia spp. Several zooplankton groups were observed to aggregate above and below the layer. With the knowledge that harmful algal bloom events can occur in subsurface thin layers, modified sampling methods to monitor for these hidden incubators could greatly improve the efficacy of early-warning systems designed to detect harmful algal blooms in coastal waters.

Marine Ecology Progress Series (MEPS)↗
USGS2021

Warming sea surface temperatures fuel summer epidemics of eelgrass wasting disease

Seawater temperatures are increasing, with many unquantified impacts on marine diseases. While prolonged temperature stress can accelerate host-pathogen interactions, the outcomes in nature are poorly quantified. We monitored eelgrass wasting disease (EWD) from 2013-2017 and correlated mid-summer prevalence of EWD with remotely sensed seawater temperature metrics before, during, and after the 2015-2016 marine heatwave in the northeast Pacific, the longest marine heatwave in recent history. Eelgrass shoot density declined by 60% between 2013 and 2015 and did not recover. EWD prevalence ranged from 5-70% in 2013 and increased to 60-90% by 2017. EWD severity approximately doubled each year between 2015 and 2017. EWD prevalence was positively correlated with warmer temperature for the month prior to sampling while EWD severity was negatively correlated with warming prior to sampling. This complex result may be mediated by leaf growth; bigger leaves may be more likely to be diseased, but may also grow faster than lesions, resulting in lower severity. Regional stressors leading to population declines prior to or early in the heatwave may have exacerbated the effects of warming on eelgrass disease susceptibility and reduced the resilience of this critical species.

Marine Ecology Progress Series↗
USGS2022

Dermal denticle shedding rates vary between two captive shark species

Shark dermal scale (denticle) accumulation in the fossil record can provide information about the abundance and composition of past shark communities. Denticles are shed continuously, such that a single shark leaves a scattered composite of many isolated denticles in sediments. However, the rate of denticle shedding as well as how these rates vary among shark species with different life modes and their consistency over time are unknown, limiting the interpretation of denticle assemblages. To better understand the process of denticle shedding and calibrate the relationship between absolute shark abundance in the environment and denticle deposition in sediments, we captured denticles shed by 2 shark species in a large aquarium over 9 mo. We then simulated how these aquarium-derived shedding rates shape the relationship between shark abundance and denticle accumulation. Bonnethead sharks Sphyrna tiburo , a more active, benthopelagic species with small, thin denticles, shed 3.6 times faster on average than zebra sharks Stegostoma fasciatum , a more sedentary, demersal species with large, robust denticles. This pattern persisted when shedding rates were corrected by estimated denticle quantities, shark space use, and methodological factors (2.2- to 3.8-fold difference). Over the study, bonnethead shark shedding rates declined while zebra shark shedding rates increased slightly. Finally, denticle assemblage composition corresponded with the relative abundance of denticles on the body of each species, consistent with natural shedding rather than selective loss. Overall, we show that shark taxa contribute unevenly to the denticle record, indicating that shedding rate measurements can help inform and constrain ecological interpretations of denticle assemblages.

Marine Ecology Progress Series↗
USGS2022

Phoretic sharksuckers (Echeneis naucrates) associated with an elasmobranch host occupy higher relative trophic positions

The relationship between phoretic diskfishes and their hosts is a classic example of marine symbiosis, yet surprisingly few studies have quantified this trophic relationship. We investigated the hypothesis that by consuming host parasites and prey scraps phoretic diskfishes (Echeneidae) feed at a higher relative trophic position than free-living individuals through expanded foraging opportunities. We used carbon and nitrogen stable isotope analysis of muscle tissue from both free-living and commensal sharksuckers Echeneis naucrates and their hosts, supplemented with gut-content analysis, to investigate this hypothesis. Our analysis revealed that commensal sharksuckers likely occupy higher relative trophic positions than free-living sharksuckers. The importance of scavenging host prey decreased ontogenetically as sharksuckers shifted from symbiotic phoresis to free-swimming behavior, leading to an ontogenetic change in which obligately commensal juveniles occupy higher trophic positions than free-living adults which are only facultatively commensal. Relative differences in δ 13 C and δ 15 N among individual host-commensal pairs varied among host species, suggesting potential differences in foraging opportunities among host taxa.

Marine Ecology Progress Series↗
USGS1996

Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis

Laboratory experiments employing radiotracer methodology were conducted to determine the assimilation efficiencies from ingested natural seston, the influx rates from the dissolved phase and the efflux rates of 6 trace elements (Ag, Am, Cd, Co, Se and Zn) in the mussel Mytilus edulis. A kinetic model was then employed to predict trace element concentration in mussel tissues in 2 locations for which mussel and environmental data are well described: South San Francisco Bay (California, USA) and Long Island Sound (New York, USA). Assimilation efficiencies from natural seston ranged from 5 to 18% for Ag, 0.6 to 1% for Am, 8 to 20% for Cd, 12 to 16% for Co, 28 to 34% for Se, and 32 to 41% for Zn. Differences in chlorophyll a concentration in ingested natural seston did not have significant impact on the assimilation of Am, Co, Se and Zn. The influx rate of elements from the dissolved phase increased with the dissolved concentration, conforming to Freundlich adsorption isotherms. The calculated dissolved uptake rate constant was greatest for Ag, followed by Zn > Am = Cd > Co > Se. The estimated absorption efficiency from the dissolved phase was 1.53% for Ag, 0.34% for Am, 0.31% for Cd, 0.11% for Co, 0.03% for Se and 0.89% for Zn. Salinity had an inverse effect on the influx rate from the dissolved phase and dissolved organic carbon concentration had no significant effect on trace element uptake. The calculated efflux rate constants for all elements ranged from 1.0 to 3.0% d-1. The route of trace element uptake (food vs dissolved) and the duration of exposure to dissolved trace elements (12 h vs 6 d) did not significantly influence trace element efflux rates. A model which used the experimentally determined influx and efflux rates for each of the trace elements, following exposure from ingested food and from water, predicted concentrations of Ag, Cd, Se and Zn in mussels that were directly comparable to actual tissue concentrations independently measured in the 2 reference sites in national monitoring programs. Sensitivity analysis indicated that the total suspended solids load, which can affect mussel feeding activity, assimilation, and trace element concentration in the dissolved and particulate phases, can significantly influence metal bioaccumulation for particle-reactive elements such as Ag and Am. For all metals, concentrations in mussels are proportionately related to total metal load in the water column and their assimilation efficiency from ingested particles. Further, the model predicted that over 96% of Se in mussels is obtained from ingested food, under conditions typical of coastal waters. For Ag, Am, Cd, Co and Zn, the relative contribution from the dissolved phase decreases significantly with increasing trace element partition coefficients for suspended particles and the assimilation efficiency in mussels of ingested trace elements; values range between 33 and 67% for Ag, 5 and 17% for Am, 47 and 82% for Cd, 4 and 30% for Co, and 17 and 51% for Zn.

Marine Ecology Progress Series↗
USGS2022

Estimating Pacific walrus abundance and survival with multievent mark-recapture models

Arctic marine ecosystems are undergoing rapid physical and biological change associated with climate warming and loss of sea ice. Sea ice loss will impact many species through altered spatial and temporal availability of resources. In the Bering and Chukchi Seas, the Pacific walrus Odobenus rosmarus divergens is one species that could be impacted by rapid environmental change, and thus, population assessments are needed to monitor changes in the status of this ecologically and culturally important marine mammal. We conducted a 5 yr genetic mark-recapture study to estimate demographic parameters for the Pacific walrus. We developed a Bayesian multievent mark-recapture model to estimate walrus survival and abundance while accounting for age misclassification. We estimated the probability of juvenile annual survival as 0.63 (95% credible interval [CrI]: 0.39-0.87) and adult female annual survival as 0.90 (95% CrI: 0.74-1.00). We estimated total abundance as 257 193 (95% CrI: 171 138-366 366). We provide the first estimate of total Pacific walrus abundance since an aerial survey in 2006, which generated a substantially less precise total population size estimate (129 000; 95% CI: 55 000-507 000). The emerging ecosystem state in the northern Bering and Chukchi Seas will likely result in a decline in Pacific walrus abundance, but there is substantial uncertainty regarding the magnitude of the anticipated decline. Our demographic estimates provide critical information to evaluate future population trends of this subsistence resource vital to communities that border the Bering and Chukchi Seas in the USA and Russia.

Alaska↗
USGS2022

Laysan albatross exhibit complex behavioral plasticity in the subtropical and subarctic North Pacific Ocean

Animals that regularly traverse habitat extremes between the subtropics and subarctic are expected to exhibit foraging behaviors that respond to changes in dynamic ocean habitats, and these behaviors may facilitate adaptations to novel and changing climates. During the chick-provisioning stage, Laysan albatross Phoebastria immutabilis parents regularly undertake short- and long-distance foraging trips throughout the vast central North Pacific Ocean. We examined GPS tracking data among chick-provisioning albatrosses in Hawai‘i to characterize habitats during short- and long-distance trips. The study period encompassed a marine heatwave (2014) and the cooling period after an extreme El Niño event (2016), enabling us to examine foraging habitats under novel and changing climates. First passage time and generalized additive mixed models indicated that during 183 short and 110 long trips (n = 32 birds), wind-assisted flight efficiency, proximity to productive areas, and moonlit-searching were important in both subtropical and subarctic habitats. Laysan albatross took foraging trips that had similar lengths and durations in 2014 and 2016 and visited similar areas, indicating that their foraging range did not expand in response to climatic variability. A strategy that uses similar foraging areas across years combined with reliance on environmental processes that enhance flight efficiency (wind) and that enable searching behaviors (moonlight) indicate that Laysan albatross exhibit complex behavioral plasticity that allows them to utilize subtropical and subarctic habitats affected by dynamic climate variability. This strategy may benefit their ability to respond to oceanographic and climatic change, including expanding warm water regions and changing atmospheric conditions influenced by global warming.

Alaska, Hawaii↗
USGS2024

Lingering impacts of the 2014-2016 northeast Pacific marine heatwave on seabird demography in Cook Inlet, Alaska (USA)

A protracted period (2014-2016) of anomalously warm water in the northeast Pacific Ocean precipitated an extensive die-off of common murres Uria aalge (hereafter ‘murres’) during 2015-2016, accompanied by reduced colony attendance and reproductive success of murres and black-legged kittiwakes Rissa tridactyla (‘kittiwakes’) starting in 2015. Most murres died of starvation following a large-scale reduction in abundance and quality of forage fish. To assess murre and kittiwake recovery following the marine heatwave, we monitored their demographics at 2 colonies (Chisik and Gull Islands) in Cook Inlet, Alaska (USA), from 2016 to 2019. Compared to historic data (1995-1999), we observed declines and increased variability in colony attendance and productivity across species and colonies, and predation was widespread. At Chisik, where food limitations were common during historic studies, both species experienced substantial population declines and reproductive failures in all 4 years (2016-2019) following the heatwave. At Gull, a typically productive colony during historic studies, murres failed to fledge chicks for 3 years (2016-2018) following the heatwave. By 2019, murre productivity recovered to about half that observed during historic studies (0.28 vs. 0.54 chicks per pair), but populations had declined by half. Kittiwake population size at Gull declined a quarter from historic counts, and reproduction alternated between complete breeding failures (2016/2018) and high productivity (2017/2019). These multi-year demographic impacts indicate lingering effects of the heatwave on kittiwakes and murres through forage fish depletion and increased predator disturbance, and possibly other stressors. It remains unknown whether populations can rebound to historic levels. If so, recovery would likely take decades.

Alaska↗
USGS2022

Direct and indirect pathways for environmental drivers of hatching success in the loggerhead sea turtle

Nest site selection has consequences for hatching success by mediating the temperature and moisture conditions that eggs experience during the incubation period. Understanding the potentially complex pathways by which nest placement influences these abiotic mediators, and therefore hatching success, is important for predicting which nests will be successful and which may require management action. We studied the effects of loggerhead sea turtle (Caretta caretta) nest site selection on hatching success by linking nest placement characteristics to hatching success through a structural equation model. We monitored 170 nests on Ossabaw Island, Georgia, during the summers of 2017 and 2018 and tracked nest conditions throughout the incubation period. Temperature had a complex effect on hatching success—nests had higher hatching rates if they were exposed to higher mean temperatures but also if they experienced both extremely high (>34°C) and extremely low (<26.5°C) temperatures, suggesting that temperature variability plays a role in determining nest outcomes beyond the mean temperature. Likewise, hatching success declined with a higher incidence of nests being inundated by tides. We found that nests placed at the highest elevations had the highest hatching success rates, likely because those nests had a much lower chance of being washed over by high tides and had higher mean temperatures. Nests were also more successful when placed in greater amounts of vegetation, again because vegetated nests were generally warmer and were associated with fewer washover events. These results shed light on the mechanisms behind selection for certain nest site characteristics and can guide the relocation of nests as a conservation action.

Georgia↗