Warm Summer Water Temperatures Research Articles

Wild populations of Pacific oysters (Magallana gigas) emerge during the blob heatwave in south Puget Sound, Washington USA

Marine heatwaves have altered ecosystems globally, including changing community composition and facilitating the spread of invasive species. In south Puget Sound, Washington (USA), non-native Pacific oysters (Magallana gigas) have been farmed extensively for almost a century and grown in enhancement sites, however, they have only recently recruited in the wild. This study explores how the appearance of Pacific oysters was related spatially (eight sites) and temporally (decade) to warmer summer water temperatures in south Puget Sound and compares oyster persistence across five sites where recruitment occurred. The largest recruitment event from 2012-2020 was in the summer of 2015, in the middle of the east Pacific Blob marine heatwave which led to warm water temperatures off the west coast of North America. Throughout the study period, the number of oyster recruits each year was positively correlated with warmer water temperatures. Oyster population densities differed across the five sites where recruitment occurred and generally declined after 2015, but showed no site by year interactions, which is consistent with spatially-variable recruitment and similar post-recruitment survival. Mean oyster shell heights also differed among sites, which could reflect different growth trajectories or recreational harvest patterns. This study supports the claim that warming sea surface temperatures may interact with species introductions to change modern biogeography.

Hydrodynamics of a large lake with complex geometry and topography: Lake of the Woods

We developed a high-resolution (250 m) three-dimensional hydrodynamic model of Lake of the Woods (LoW) to study surface seiches, lake circulation, and water temperature. LoW spans over two different geological regions, experiences wind variability, encompasses >14,500 islands and includes twelve hydraulically connected sub-basins. The complex geometry and topography are unique for this large lake that suffers from seasonal algal blooms. The model uses a spatially and temporally variable wind field, heat fluxes, riverine inflows obtained from a watershed model, outflows at Kenora and Norman dams, and was run for the spring-summer of 2017 and 2018. The predominant physical processes in LoW are surface seiches, and wind and rivers drive mean lake-wide circulations and mixing. The observed periods of seiches in the lake are 9.5, 3.4, 2.3, and 1.3 h, attributed to horizontal modes 1, 3, 6, and 12, respectively. Amphidromic structures show that sub-basin seiche's responses to wind may be limited to one sub-basin; however, lake-wide responses were also observed, which suggests the seiche-induced oscillatory velocities can impact transport paths. The mean water temperature is variable spatially, ranging from <15 °C in early June to ∼25 °C in July-August. Sabaskong Bay experienced warmer summer water temperatures with unidirectional mean flows to the lake. Main water transport is towards the northeast. Modelled conservative tracers, consistent with observations, show that the Rainy River plume extent covers Big Traverse, Morson, and Little Traverse Bays. The modelled seasonal hydraulic retention times in southern bays are <150 days and are much longer in northern bays.

Lakes in Hot Water: The Impacts of a Changing Climate on Aquatic Ecosystems.

Our planet is being subjected to unprecedented climate change, with far-reaching social and ecological repercussions. Below the waterline, aquatic ecosystems are being affected by multiple climate-related and anthropogenic stressors, the combined effects of which are poorly understood and rarely appreciated at the global stage. A striking consequence of climate change on aquatic ecosystems is that many are experiencing shorter periods of ice cover, as well as earlier and longer summer stratified seasons, which often result in a cascade of ecological and environmental consequences, such as warmer summer water temperatures, alterations in lake mixing and water levels, declines in dissolved oxygen, increased likelihood of cyanobacterial algal blooms, and the loss of habitat for native cold-water fisheries. The repercussions of a changing climate include impacts on freshwater supplies, water quality, biodiversity, and the ecosystem benefits that they provide to society.

Ecological risk assessment of environmental stress and bioactive chemicals to riverine fish populations: An individual-based model of smallmouth bass Micropterus dolomieu✰

• A modeling framework is developed to assess population-level effects of temperature, flow and chemicals. • The framework includes three modules: biological model module, effect module and population model. • The framework is demonstrated with an individual-based model of smallmouth bass. • Warm summer water temperatures and year-round high flows have the most severe impacts. • Exposure to estrogenic endocrine disrupting compounds substantially reduces population size. Ecological risk assessments play an important role in environmental management and decision-making. Although empirical measurements of the effects of habitat changes and chemical exposure are often made at molecular and individual levels, environmental decision-making often requires the quantification of management-relevant, population-level outcomes. In this study, we generalized a modeling framework to evaluate population-level ecological risk of environmental stress and bioactive chemicals. The modeling framework includes (1) a biological model module that incorporates complex and interacting biological and ecological processes, and environmental stochasticity, (2) an effect module that links the impacts of environmental changes and chemical exposure to individual characteristics, and (3) a population module that makes decisions on the choice of population-level properties to best capture the effects and thus to track in the model based on the target species and the research and management interest. This framework is a 3-module procedure that provides an alternative way for researchers to organize, present and communicate the risk assessment modeling studies. To demonstrate this framework, we used a socioeconomically important riverine fish species, smallmouth bass Micropterus dolomieu , as the model species. We developed an individual-based model as the biological model module. We evaluated the impacts of changing water temperature and flow regimes, and the impacts of exposure to estrogenic endocrine disrupting compounds (EEDC) on smallmouth bass populations in the Chesapeake Bay Watershed, USA. Warm summer water temperatures and year-round high flows had the most severe impacts on the smallmouth bass population. An increase in exposure level to EEDC, both year-round and in summer months, substantially reduced population size, spawner and recruit abundance, and the proportion of quality-length individuals. Acute exposure to EEDC was more detrimental to the population than chronic exposure. Acute exposure during spawning season had the most severe impacts. This modeling framework can be extended to other species, environmental factors and chemicals, and can be used to inform management and conservation decisions.

Asian carp spawning success: Predictions from a 3-D hydrodynamic model for a Laurentian Great Lake tributary

Asian carps are threatening to establish in the Great Lakes basin and the examination of factors leading to spawning success is vital for preventive efforts. Hydrodynamic modelling can determine if successful hatching of carp eggs can occur in a tributary, by predicting egg movement during a spawning event to see if hatching can occur before eggs settle. A 3-D hydrodynamic model, coupled with a Lagrangian particle tracker, was used to assess hatching rates of three Asian carp species (bighead, grass, and silver carps) in different temperature and flow scenarios in the east Don River, a potential spawning tributary to Lake Ontario. In-river hatching rates were highest in scenarios with warmer summer water temperatures (23–25 °C) and flow magnitudes of 15–35 m3/s, which occur at least once every year. Using a 3-D hydrodynamic model allowed the inclusion of low-velocity zones where eggs become trapped in lower flow scenarios, thereby reducing modelled hatching success. In-river hatching rates were significantly reduced when the spawning location was moved close to the mouth of the river, with no modelled hatching if spawning occurred in the lower 8 km of the Don River, indicating that preventing Asian carp movement upstream would viably reduce the chances of successfully spawning occurring in this tributary. The magnitude of reduction in spawning success caused by limiting Asian carp passage upstream can guide preventative strategies and the method of using a 3-D hydrodynamic model as a predictive tool could be applied in similar tributaries across the Great Lakes basin.

Eco solution increases fish rehabilitation

The Bull Run Watershed is the primary drinking water supply for the City of Portland in the US. It also plays an important role in supporting the larger aquatic ecosystem of the Sandy and Lower Columbia rivers where, due to warm summer water temperatures, some of the fish species have recently been in significant decline.

Climate Change and the Delta

Anthropogenic climate change amounts to a rapidly approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to challenge these management and ecological systems in different ways that are characterized by different levels of uncertainty. For example, there is high certainty that climate will warm by about 2°C more (than late-20th-century averages) by mid-century and about 4°C by end of century, if greenhouse-gas emissions continue their current rates of acceleration. Future precipitation changes are much less certain, with as many climate models projecting wetter conditions as drier. However, the same projections agree that precipitation will be more intense when storms do arrive, even as more dry days will separate storms. Warmer temperatures will likely enhance evaporative demands and raise water temperatures. Consequently, climate change is projected to yield both more extreme flood risks and greater drought risks. Sea level rise (SLR) during the 20th century was about 22 cm, and is projected to increase by at least 3-fold this century. SLR together with land subsidence threatens the Delta with greater vulnerabilities to inundation and salinity intrusion. Effects on the Delta ecosystem that are traceable to warming include SLR, reduced snowpack, earlier snowmelt and larger storm-driven streamflows, warmer and longer summers, warmer summer water temperatures, and water-quality changes. These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas. Although the effects of of climate change on Delta ecosystems may be profound, the end results are difficult to predict, except that native species will fare worse than invaders. Successful preparation for the coming changes will require greater integration of monitoring, modeling, and decision making across time, variables, and space than has been historically normal.

Reduced calcification in Western Australian corals during anomalously high summer water temperatures

Here we report the seasonal response of calcification rates over two years, for three coral species (Acropora pulchra, Pocillopora damicornis and Goniastrea aspera), to anomalously warm summer water temperatures (2012 and 2013), following the most severe marine heat wave on record (2010–2011). The study sites at Coral Bay (Ningaloo Reef), the Houtman Abrolhos Islands and Marmion Reef (Perth) spanned over 10° of latitude and ranged from tropical to temperate habitats. Calcification rates were determined using repeated measurements of buoyant weight normalized to surface area and rates were monitored over two winters and two summers from 2011 to 2013. Average growth rates followed predicted latitudinal trends, with the fastest growth in the tropics (Coral Bay) and slowest growth rates in the temperate zone (Marmion). However, calcification rates did not show the expected seasonality (higher in summer, lower in winter), even at high latitude locations. Instead, there was either little difference between summer and winter growth or growth was slower in the summer (on average, a reduction of ~40% across locations and species). Additionally, differences in species growth rates did not follow expected trends, with usually fast growing branching corals not calcifying much faster than the normally slower growing massive corals (A. pulchra, grew ~40% faster than G. aspera, which grew ~6% faster than P. damicornis across all latitudes and seasons). Survival rates were also reduced in the summer months, while among species, P. damicornis had the lowest survival and G. aspera the highest. We conclude that high temperature stress through the summers of 2011 to 2013 was the most likely cause for the lack of seasonality in calcification rates, the similarity in calcification rates among species and the increased mortality of susceptible species in the summer months. The effect of prolonged elevated temperature anomalies (1.5 to 3°C) on the growth and survival of colonies over consecutive years was often greater than the fundamental influences of season and species, highlighting the extent to which climate change could now be re-structuring the life histories of corals on Western Australian reefs.

Influence of Variable Interannual Summer Water Temperatures on Brook Trout Growth, Consumption, Reproduction, and Mortality in an Unstratified Adirondack Lake

AbstractStressful water temperatures negatively affect physiological processes in fishes, yet evidence for how elevated temperatures influence population‐level characteristics is rare. An 8‐year field study of brook trout Salvelinus fontinalis in an unstratified Adirondack lake revealed that an aggregate measure of chronically stressful summer water temperatures strongly influenced brook trout population‐level characteristics. We quantified chronic thermal stress using the cumulative degree‐days over which bottom temperatures exceeded a range of thresholds (18–22°C) and found that the strongest relationships were with cumulative degree‐days over 20°C (DD&gt;20). Across years with similar brook trout densities, warmer summer water temperatures resulted in decreased brook trout growth, but growth was not reduced in a year with high water temperatures and low density. Maximum stomach fullness was negatively related to water temperature. Reproductive activity was negatively correlated with stressful summer thermal conditions and was less dependent on female brook trout density. Periods of chronically stressful summer water temperatures resulted in the apparent mortality of age‐2 and older fish during a moderately stressful summer (156 DD&gt;20) and apparent mortality of age‐1 and older fish during the most stressful summer (210 DD&gt;20). In contrast, extensive mortality was not evident in any year‐classes when DD&gt;20 was less than 115. Anthropogenic impacts on the thermal conditions of aquatic ecosystems occur at small (hydrology) and large (climate change) spatial extents, and in situ studies at the margin of an organism's thermal range can provide important insights into changes that will occur if temperatures increase.

Parasitic Copepod (Lernaea cyprinacea) Outbreaks in Foothill Yellow-legged Frogs (Rana boylii) Linked to Unusually Warm Summers and Amphibian Malformations in Northern California

How climate change may affect parasite–host assemblages and emerging infectious diseases is an important question in amphibian decline research. We present data supporting a link between periods of unusually warm summer water temperatures during 2006 and 2008 in a northern California river, outbreaks of the parasitic copepod Lernaea cyprinacea, and malformations in tadpoles and young of the year Foothill Yellow-legged Frogs (Rana boylii). Relative to baseline data gathered since 1989, both 2006 and 2008 had significantly longer periods when daily mean water temperatures exceeded 20°C compared to years without copepod outbreaks. Infestation varied spatially in the watershed, as prevalence increased concomitantly with temperature along a 5.2 km longitudinal transect. At breeding sites of R. boylii with copepods in 2006, infestation ranged from 2.9% of individuals upstream to 58.3% downstream. In 2008, copepods were absent from the most upstream sites and infested up to 28.6% of individuals sampled at downstream locations. Copepods most frequently embedded near a hind limb or the cloaca. Among individuals with parasites in 2006, 26.5% had morphological abnormalities compared to 1.1% of un-infested individuals. In 2008 when the infestation peak occurred late in development (post Gosner stage 39), abnormalities were not associated with copepod infestation. In both years, recently metamorphosed frogs with copepods were, on average, slightly smaller than those not infested. These occurrences represent a sudden increase in local prevalence atypical for this river ecosystem. Previously we had only once seen copepods on amphibians (on non-native Bullfrogs, Rana catesbeiana), six km further downstream. Pacific Chorus Frogs, Pseudacris regilla, which co-occur with R. boylii in shallow near shore habitats were not used as hosts. The data suggest that increasing summer water temperatures, decreased daily discharge, or a combination of both, promote outbreaks of this non-native parasite on an indigenous host, and could present a threat to the long-term conservation of R. boylii under the flow regime scenarios predicted by climate change models.

Seasonally Dependent Movement of Lake Trout between Two Northern Idaho Lakes

The diel and seasonal movements of lake trout Salvelinus namaycush between Upper Priest Lake and Priest Lake, Idaho, were studied in 2000. Gill nets were used to capture and detect fish movements between the lakes. Lake trout were caught in the outlet of Upper Priest Lake and in the Thorofare (the narrow channel connecting the two lakes) primarily in the spring and fall, when water temperatures were cool. No lake trout were caught when the water temperature exceeded 15°C. Lake trout were primarily caught at night (94%). Multiple regression analysis indicated that nighttime lake trout catch per unit effort (CPUE) was significantly higher at lower lake surface water temperatures than at higher temperatures (P < 0.01). Daytime lake trout CPUE was significantly higher at low Priest Lake surface temperature than high temperature and at high Thorofare depth than at low depth (P < 0.01). Nighttime CPUE was significantly higher than daytime CPUE (P < 0.01). These results indicate that warm summer water temperatures function as a natural thermal barrier to movement between the lakes in July and August, and that it may be necessary to block lake trout movements between the two lakes at other times to effectively control the population in Upper Priest Lake.

EFFECTS OF CHANGING CLIMATE ON ZOOPLANKTON AND JUVENILE SOCKEYE SALMON GROWTH IN SOUTHWESTERN ALASKA

Detecting and forecasting the effects of changing climate on natural and exploited populations represent a major challenge to ecologists and resource managers. These efforts are complicated by underlying density-dependent processes and the differ- ential responses of predators and their prey to changing climate. We explored the effects of density-dependence and changing climate on growth of juvenile sockeye salmon and the densities of their zooplankton prey in the Wood River system of southwestern Alaska. We fit dynamic time-series models to data collected between 1962 and 2002 describing growth of juvenile sockeye, timing of spring ice breakup, and summer zooplankton densities. The timing of spring breakup has moved about seven days earlier now than it was in the early 1960s. Our analyses suggest that most of this shift has been a response to the warm phase of the Pacific Decadal Oscillation that persisted from the mid-1970s to the late 1990s. This progression toward earlier spring breakup dates was associated with warmer summer water temperatures and increased zooplankton (especially Daphnia) densities, which translated into increased sockeye growth during their first year of life. The number of spawning adults that produced each year class of sockeye had a strong negative effect on juvenile sockeye growth rates, so that the size of the density-dependent effect was, on average, twice as large as the effect of spring breakup date. These results highlight the complexity of eco- logical responses to changing climate and suggest that climate warming may enhance growing conditions for juvenile salmonids in large lakes of Alaska.

Burrowing saves Lake Erie clams

Freshwater unionid clams in North America have been virtually eliminated from waters that are colonized by zebra mussels. Near total mortality has been reported in western Lake Erie1,2,3,4, but we have now discovered a large population of native clams in a Lake Erie wetland that shows little sign of infestation. Field observations and laboratory experiments show that warm summer water temperatures and soft, silt-clay sediments trigger burrowing by clams. This discourages infestation and physically removes any attached zebra mussels.

Exceptionally big individual perch (Perca fluviatilis L.) and their growth

In Lake Windermere (U.K.) where there was a dense, slow‐growing population of perch (Perca fluviatilis L.) which had an lx of about 180 mm, there co‐existed a few individuals with an lx of 463 mm. Data from 137 of these big perch, mostly caught in gillnets fishing for Esox lucius L., were examined. Their early growth was identical to that of normal perch, but, at an age, varying between individuals, from 1 to 8 and averaging 4 years, their growth accelerated for about 4 years and then followed a von Bertalanffy model with an lx of 463 mm. They thus had a ‘double’ growth‐curve that is revealed only if individual growth is examined. Acceleration tended to occur in certain calendar years and was correlated with strong year‐classes of young perch. Growth was greater in years with warm summer water temperatures. There were no changes in the growth of big perch, after they had achieved 290 mm, during a period of great changes in the population density and an increase in the growth of normal perch &lt; 290 mm. No more big perch were caught in Windermere between 1967 and 1990. Net selection, length‐weight relationships, seasonal cycle in gonad weight, and opercular‐body length relationship were the same as those of normal perch. The few available data suggest that big perch were piscivorous, feeding largely on small perch. The distribution of sites in the lake where big perch were caught is contagious, catches follow the negative binomial; but within fishings that caught big perch at the same site and time, catches were more evenly distributed than random. It is postulated that most adults would have accelerated their growth if they had sustained piscivory. Similar big perch have been found in other lakes.