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USGS2017

Genomics of Arctic cod

The Arctic cod (Boreogadus saida) is an abundant marine fish that plays a vital role in the marine food web. To better understand the population genetic structure and the role of natural selection acting on the maternally-inherited mitochondrial genome (mitogenome), a molecule often associated with adaptations to temperature, we analyzed genetic data collected from 11 biparentally-inherited nuclear microsatellite DNA loci and nucleotide sequence data from from the mitochondrial DNA (mtDNA) cytochrome b (cytb) gene and, for a subset of individuals, the entire mitogenome. In addition, due to potential of species misidentification with morphologically similar Polar cod (Arctogadus glacialis), we used ddRAD-Seq data to determine the level of divergence between species and identify species-specific markers. Based on the findings presented here, Arctic cod across the Pacific Arctic (Bering, Chukchi, and Beaufort Seas) comprise a single panmictic population with high genetic diversity compared to other gadids. High genetic diversity was indicated across all 13 protein-coding genes in the mitogenome. In addition, we found moderate levels of genetic diversity in the nuclear microsatellite loci, with highest diversity found in the Chukchi Sea. Our analyses of markers from both marker classes (nuclear microsatellite fragment data and mtDNA cytb sequence data) failed to uncover a signal of microgeographic genetic structure within Arctic cod across the three regions, within the Alaskan Beaufort Sea, or between near-shore or offshore habitats. Further, data from a subset of mitogenomes revealed no genetic differentiation between Bering, Chukchi, and Beaufort seas populations for Arctic cod, Saffron cod (Eleginus gracilis), or Walleye pollock (Gadus chalcogrammus). However, we uncovered significant differences in the distribution of microsatellite alleles between the southern Chukchi and central and eastern Beaufort Sea samples of Arctic cod. Finally, using ddRAD-Seq data, we identified species-specific markers and in conjunction with mitogenome data, identified an Arctic cod x Polar cod hybrid in western Canadian Beaufort Sea. Overall, the lack of genetic structure among Arctic cod within the Bering, Chukchi and Beaufort seas of Alaska is concordant with the absence of geographic barriers to dispersal and typical among marine fishes. Arctic cod may exhibit a genetic pattern of isolation-by-distance, whereby populations in closer geographic proximity are more genetically similar than more distant populations. As this signal is only found between our two fartherest localities, data from populations elsewhere in the species’ global range are needed to determine if this is a general characteristic. Further, tests for selection suggested a limited role for natural selection acting on the mitochondrial genome of Arctic cod, but do not exclude the possibility of selection on genes involved in nuclear-mitogenome interactions. Unlike previous genetic assessment of Arctic cod sampled from the Chukchi Sea, the high levels of genetic diversity found in Arctic cod assayed in this study, across regions, suggests that the species in the Beaufort and Chukchi seas does not suffer from low levels of genetic variation, at least at neutral genetic markers. The large census size of Arctic cod may allow this species to retain high levels of genetic diversity. In addition, we discovered the presence of hybridization between Arctic and Polar cod (although low in frequency). Hybridization is expected to occur when environmental changes modify species distributions that result in contact between species that were previously separated. In such cases, hybridization may be an evolutionary mechanism that promotes an increase in genetic diversity that may provide species occupying changing environments with locally-adapted genotypes and, therefore, phenotypes. Natural selection can only act on the standing genetic variation present within a population. Therefore, given its higher levels of genetic diversity in combination with a large population size, Arctic cod may be resilient to current and future environmental change, as high genetic diversity is expected to increase opportunities for positive selection to act on genetic variants beneficial in different environments, regardless of the source of that genetic variation.

OCS Study↗

USGS2014

Proper handling of animal tissues from the field to the laboratory supports reliable biomarker endpoints

In the endeavor to assess potential effects to the Gulf of Mexico ecosystem from the Mississippi Canyon 252 incident, referred to as the Deepwater Horizon oil spill, various environmental data have been collected. Whereas initial efforts have included satellite tracking and sediment and water sampling to estimate the geographical scope of oiling, research on biological samples can provide insights into potential physiological responses to oil if it was present in the food web, sediment, or water column. Fish species are ideal model organisms for studying responses to water- and sediment-borne contaminants due to their life history (Jenkins et al. 2014), and several Gulf of Mexico fish species were studied by scientists after this incident. Typical field data collected on fish reflect organism condition and include observations such as fish length, weight, gonad condition, condition factor (weight in relation to length), parasite load, and color of organs (Schmitt and Dethloff 2000). However, if physiological responses occurred due to oil exposure, effects would not be immediately visible using organism-level observations alone. Changes occur first at the organ, tissue, cell, or molecular levels, and these responses can be measured by using biomarker assays (van der Oost et al. 2003).

Book chapter↗

USGS2018

Smallmouth bass predation on subyearling fall Chinook salmon in Lower Granite Reservoir, 2016–2017

Predation by nonnative fishes is one factor that has been implicated in the decline of juvenile salmonids in the Pacific Northwest. Impoundment of much of the Snake and Columbia Rivers has altered food webs and created habitat favorable for species such as smallmouth bass Micropterus dolomieu. Smallmouth bass are common throughout the Columbia River basin and have become the most abundant predator in lower Snake River reservoirs (Zimmerman and Parker 1995). This is a concern for Snake River fall Chinook salmon Oncorhynchus tshawytscha (hereafter, subyearlings) that may be particularly vulnerable due to their relatively small size and because their main-stem rearing habitats often overlap or are in close proximity to habitats used by smallmouth bass (Curet 1993; Tabor et al. 1993). Concern over juvenile salmon predation spawned a number of large-scale studies to quantify its effect in the late 1980s, 1990s, and early 2000s (Poe et al. 1991; Rieman et al. 1991; Vigg et al. 1991; Fritts and Pearsons 2004; Naughton et al. 2004). Smallmouth bass predation represented 9% of total salmon consumption by predatory fishes in John Day Reservoir, Columbia River, from 1983 through 1986 (Rieman et al. 1991). In transitional habitat between the Hanford Reach of the Columbia River and McNary Reservoir, juvenile salmon (presumably subyearlings) were found in 65% of smallmouth bass (>200 mm) stomachs and comprised 59% of the diet by weight (Tabor et al. 1993). Within Lower Granite Reservoir on the Snake River, Naughton et al. (2004) showed that monthly consumption (based on weight) ranged from 5% in the upper reaches of the reservoir to 11% in the forebay. However, studies in the Snake River were conducted soon after Endangered Species Act (ESA) listing of Snake River fall Chinook salmon (NMFS 1992). During this time, fall Chinook salmon abundance was at an historic low, which may explain why consumption rates were relatively low compared to those from studies conducted in the Columbia and Yakima Rivers where abundance was higher (e.g., Tabor et al. 1993; Fritts and Pearsons 2004). We speculate that predation on subyearlings by smallmouth bass in the Snake River may have increased in recent years for several reasons. Since their ESA listing, recovery measures implemented for Snake River fall Chinook salmon have resulted in a large increase in the juvenile population (Connor et al. 2013). Considering that subyearlings probably now make up a larger portion of the forage fish population, it is plausible they should make up a larger portion of smallmouth bass diets. Second, migrating subyearlings delay downstream movement in the transition zones of the Clearwater River and Snake River for varying lengths of time (Tiffan et al. 2010), which increases their exposure and vulnerability to predators. Spatial overlap in locations of smallmouth bass and subyearlings that died during migration provides support for this (Tiffan et al. 2010). Finally, the later outmigration of subyearlings from the Clearwater River results in their presence in Lower Granite Reservoir during the warmest summer months when predation rates of smallmouth bass should be highest. In 2016 and 2017, we focused our smallmouth bass predation efforts in Lower Granite Reservoir downstream of the transition zones and the confluence area where we worked during 2012–2015. This report primarily covers results from 2017 but some results from 2016 are also included for comparison. Similar to past years, our first objective was to quantify smallmouth bass consumption rates of subyearlings, determine bass abundance, and describe bass diets. In addition, Tiffan et al. (2016a) posited that predation risk to subyearlings may be higher in shoreline habitats that are more suitable for smallmouth bass and lower in shoreline habitats that are more suitable for subyearlings. To test this hypothesis, our second objective was to examine the relationship between smallmouth bass predation and subyearling habitat suitability. Our final objective was to combine estimates of consumption with smallmouth bass abundance to derive estimates of total Chinook salmon losses to smallmouth bass for 2016 and 2017.

Idaho, Washington↗

USGS2019

Polychlorinated biphenyls (PCBs) in the Pacific sand lance, Puget Sound, Washington

Forage fish are small, abundant, schooling planktivores that form a critical link in marine food webs by transferring energy from plankton up to birds, fishes, and marine mammals. Forage fishes in Puget Sound include the iconic Pacific herring as well as lesser known species such as surf smelt and the Pacific sand lance. There are significant knowledge gaps regarding the basic life history and population status of Pacific sand lance and no information regarding potential stressors such as contaminants.

Washington↗

USGS2018

Describing the distribution and productivity of biota along a nearshore to offshore gradient

The Lake Michigan Lakewide Action and Management Plan (LAMP) proposed adding nutrients (phosphorus) to its “pollutant of concern” list in 2002, given that excessive nutrients were causing impairments in nearshore waters. Since that time, scientists have highlighted the “shunting” of nutrients to the nearshore (Hecky et al. 2004), owing to the ability of invasive dreissenid mussels to capture some portion of allochthonous phosphorus that enters the lake through tributaries. These changes are believed to increase productivity in the nearshore, reflected in increased benthic and pelagic primary production and nuisance Cladophora (Auer et al. 2010). Whether increases in primary productivity lead to concomitant increases for secondary (by zooplankton) and tertiary (by fish) production remains largely untested. Hence, understanding the distribution and abundance of nutrients and biota (e.g., zooplankton, fish) across a nearshore to offshore gradient was identified as a Cooperative Science and Monitoring Initiative (CSMI) priority in 2015. Increased understanding of the Lake Michigan nearshore will also facilitate the development of a Nearshore Strategy by the LAMP, which is called for in the 2012 Great Lakes Water Quality Agreement. Working collaboratively with Environmental Protection Agency (EPA) and National Oceanic and Atmospheric Administration (NOAA), United States Geological Survey (USGS) described the distribution of nutrients and biota across nearshore to offshore transects in 2015 (see Appendix 1). At each transect, we sampled the food web at three sites with differing bottom depths: 18 m, 46 m, and 91-110 m. We purposefully chose transects near tributaries of varying total phosphorus (TP) input (see Figure 1, Dolan and Chapra 2012): three transects that were not associated with any large tributary where total phosphorus would be loaded (Waukegan IL, Frankfort MI, Sturgeon Bay WI), three transects adjacent to tributaries presumed to be relatively low loaders of TP (Pere Marquette MI, Root WI, Muskegon MI), and three transects adjacent to tributaries presumed to be relatively high loaders of TP (St. Joseph MI, Kalamazoo MI, Manitowoc WI). USGS estimated chlorophyll concentrations, zooplankton, Mysis , larval fish, and juvenile and adult fish seasonally (April/May, July, October/November) at eight of these transects (all but Muskegon).

Illinois, Michigan, Wisconsin↗

USGS2020

How and why is the timing and occurrence of seasonal migrants in the Gulf of Maine changing due to climate?

Plants and animals undergo certain recurring life-cycle events, such as migrations between summer and winter habitats or the annual blooming of plants. Known as phenology, the timing of these events is very sensitive to changes in climate (and changes in one species’ phenology can impact entire food webs and ecosystems). Shifts in phenology have been described as a “fingerprint” of the temporal and spatial responses of wildlife to climate change impacts. Thus, phenology provides one of the strongest indicators of the adaptive capacity of organisms (or the ability of organisms to cope with future environmental conditions). In this study, researchers are exploring how the timing and occurrence of a number of highly migratory marine animals is changing due to a series of climatic and ecological shifts. First, using existing long-term historical data series, they will determine the direction and magnitude of how migration, abundance, or other phenological factors have changed for marine mammals, sea turtles, and fishes that migrate into the Gulf of Maine on a seasonal basis. Because marine animals are inherently difficult to detect, the team will apply dynamic occupancy models to evaluate seasonal migration patterns and habitat use across multiple habitats in the Gulf of Maine region. The project team will also synthesize regional information on a key, ecologically-important prey fish, sandlance, whose timing and abundance is a strong predictor of the occurrence and behavior of predator species targeted in this study as well as a range of other regional fish and wildlife of conservation and management concern. Results from this component of the project will identify coastal fish and wildlife species that are relatively more or less able to adapt and thus potentially vulnerable to climate change; determine the likely primary drivers of those changes; and identify data gaps and future monitoring needs. Ultimately, this information will be available and useful for regional coastal management and adaptation decisions that will allow managers to effectively plan for the future. In a second component of the project, researchers will focus specifically on changes in migration patterns of the endangered North Atlantic right whale. While shifts in the distribution and time of recurring life events are adaptive responses that may help species cope with climate impacts, they can also lead to changes in how species interact with humans. The North Atlantic right whale is one of the most endangered whale species on the planet. In the North Atlantic Ocean, ship strikes and entanglements with commercial fishing gear represent fatal threats to right whales. Recent reports suggest that North Atlantic right whale migration patterns have changed. Many researchers posit that shifts in migration are responsible for recent increases in the overlap between right whales and human activities, especially fishing. To help understand how changes in right whale movements and behaviors may overlap with ship traffic, and thus put the animals at risk of encountering vessels, we will combine right whale habitat models with ship traffic maps. The end result will be a set of maps identifying risk levels.

Gulf of Maine↗

USGS2020

Ratios of methylmercury to total mercury in predator and primary consumer insects from Adirondack streams in New York State

Mercury (Hg) is a global pollutant that affects aquatic biota in otherwise pristine settings such as the Adirondack region of New York State. Bioaccumulation of Hg is especially problematic in sensitive landscapes, where inorganic mercury from atmospheric deposition is readily converted, via natural processes, to methylmercury (MeHg), the toxic form that is taken up and biomagnified in aquatic food webs. There is great interest in monitoring MeHg in aquatic biota across these sensitive regions to evaluate responses to changes in Hg emissions. Aquatic insects, such as dragonfly larvae, have great potential as MeHg “biosentinels,” but currently are not widely used for this purpose. An important practical consideration in the use of aquatic insects for MeHg biomonitoring is whether total mercury (THg) is a suitable surrogate for MeHg, which is much more technically challenging and expensive to analyze than is THg. The objective of this project was to assess the suitability of THg as a surrogate for MeHg in stream-dwelling insects. Specifically, existing data on immature aquatic insects from nine Adirondack streams were used to characterize MeHg to THg ratios (i.e., MeHg%), and variation in these ratios (e.g., among sites, seasons, taxa) in predator and primary consumer insects, examine how well THg in different groups tracks measured stream water MeHg (i.e., filtered MeHg; FMeHg), and explore the influence of trophic position (indicated by nitrogen stable isotopes; δ 15 N) on the observed MeHg% patterns. Three broad insect feeding groups were included in this analysis: predators, shredders, and scrapers. Predators had the highest MeHg% (median 94%), and MeHg% did not differ significantly among any of the taxa considered: stoneflies, damselflies, and three families of dragonflies (darners, common skimmers, and clubtails). Darners and common skimmers, the most numerous and abundant predators, were combined for further analyses. Site medians for these “selected dragonflies” were all at least 90% (summer-fall collections) and MeHg% did not differ significantly among sites. The correlation between FMeHg and THg in selected dragonflies was nearly as strong as that of FMeHg and dragonfly MeHg. In contrast, median MeHg% in shredders (northern caddisflies) and scrapers (flathead mayflies), which are both primary consumers, was lower overall (medians 52% and 35%, respectively), more variable, and less-well representative of FMeHg than predators. Stable isotope results indicate that variation in feeding position is an important influence on some of the MeHg% patterns observed in this study. This study’s findings suggest that THg is likely to be a suitable surrogate for MeHg in predatory aquatic insects from Adirondack streams, but do not support the use of THg in primary consumers for regional MeHg monitoring.

New York↗

USGS2021

Status of Cisco in Lake Superior in 2017

This report describes the status of fish species and their habitat in Lake Superior during the reporting period of 2012-2016 in response to achievement of fish community objectives (FCOs) established by fishery managers for the lake. The overarching goal for the FCOs continued to be met as the fish community remained diverse, self-regulating, dominated by indigenous species, and able to support sustainable fisheries, although further rehabilitation of certain fish is required. The Lake Superior Lakewide Action and Management Plan classified all habitat indicators for Lake Superior as good. Primary production and zooplankton abundance were stable during the reporting period and unchanged from the two previous reporting periods, indicating the lower food web is healthy. Abundance of the invertebrates Mysis diluviana and Diporeia spp. were stable during the reporting period, and Diporeia spp. density exceeded target levels defined in the Great Lakes Water Quality Agreement. Lake Whitefish (Coregonus clupeaformis) abundance was lower than during the previous reporting period but was within the FCO target. Abundance of lean, siscowet, and humper forms of Lake Trout (Salvelinus namaycush) remained stable at levels seen in previous reporting periods. The FCO for non-indigenous salmonids was met as Chinook Salmon (Oncorhynchus tshawytscha), Coho Salmon (O. kisutch), and steelhead/Rainbow Trout (O. mykiss) were being sustained by natural reproduction, and their abundance remained stable or increased from previous reporting periods. The FCO for Walleye (Sander vitreus) was not met, although populations showed signs of improvement since the previous reporting period. The fish community in littoral areas and embayments continued to be diverse and composed mostly of indigenous species. No new invasive species were found in Lake Superior during the reporting period. Degraded embayment and tributary habitats continued to prevent achievement of the FCOs for Brook Trout (S. fontinalis) and Lake Sturgeon (Acipenser fulvescens). Barriers created for hydroelectric generation either blocked Lake Sturgeon from historically important spawning grounds or reduced stream flows necessary for its reproduction. In tributaries without man-made barriers, Lake Sturgeon was relatively abundant and appeared healthy. Attainment of the FCOs for Brook Trout and Lake Sturgeon will be challenging and can only be attained through development of large-scale management actions like those implemented for Lake Trout rehabilitation and Sea Lamprey (Petromyzon marinus) control. Sea Lamprey-control expenditures doubled in 2016 from past levels and should result in suppression of the population closer to its FCO after 2016. The prey-fish FCO appears to have been met, but biomass of nearly all prey-fish species declined from that reported for the previous reporting period and has been on a downward trajectory since 2000. Predation by Lake Trout is probably to blame for the declining biomass of prey fish. Poor recruitment by Cisco (C. artedi) over the last 15 years is exacerbating the declines in prey-fish biomass because Lake Trout must compensate for the loss of Cisco by consuming other, less-abundant prey fish.

Lake Superior↗

USGS2021

State of Lake Superior ecosystem in 2017

Lake Superior↗

USGS2021

Monitoring the recovery of seabirds and forage fish following a major ecosystem disruption in Lower Cook Inlet

Following the North Pacific marine heatwave of 2014-2016 and associated extreme die-off of seabirds in the winter of 2015-2016, we repeated historical marine bird and forage fish surveys around two seabird colonies (Gull Island, Chisik Island) in lower Cook Inlet during 2016-2019 in order to document immediate and lingering impacts of the heatwave on resident fish and seabird populations. At sea, we conducted acoustic/trawl surveys for fish in near-colony areas, while simultaneously counting seabirds on survey transects. At colonies, we monitored bird numbers on whole colony censuses and population plot counts and assessed annual reproductive success of Black-legged Kittiwakes ( Rissa tridactyla ) and Common Murres ( Uria aalge ). Our studies suggest that impacts of the heatwave on seabirds and their forage base were severe and extended for several years beyond the heatwave itself. Although fish biomass indices were greatest in 2016-2017, the forage community was largely dominated by juvenile fish with low nutritional value following a collapse of key species of forage fish during the marine heatwave. Lowest fish biomass was observed in 2018, coincident with a marked decline in the at-sea abundance of many seabirds around colonies. By 2019 there were signs of improvement in prey abundance and quality, and significant aggregations of pre-spawning capelin and large sand lance were observed in and around Kachemak Bay. In comparison with historical (1996-1999) bird colony surveys, kittiwake population counts decreased by more than 70% at Chisik Island, and by 8-29% at Gull Island. Similarly, murre counts decreased at Chisik Island by 72% and by more than 20% at Gull Island. Kittiwakes had complete reproductive failure at Chisik Island from 2016-2018, with minimal success in 2019. At Gull Island, kittiwakes also failed in 2016 and 2018 but had unusually high productivity in 2017 and 2019. Murres also had complete reproductive failures at Chisik Island in all four years and at Gull Island during 2016, 2017 and 2018. Murres finally fledged chicks in 2019, albeit at about half the normal rate. Finally, we also observed unusually high levels of predator disturbance (egg predation, flushing adults from plots) and unprecedented numbers of adult birds in poor body condition (“skinny murres”), particularly in 2018. Together, these results indicate that an extreme disruption of marine food webs occurred during and after the heatwave. Given the prolonged reproductive failures, continued monitoring is required to assess continuing impacts and recovery from the 2014-2016 heatwave. For example, murre chicks that would have been produced in 2016 should, after 4-5 years away, start recruiting to the colony in 2021, and thereby replace aged adults that would have died naturally in the past year(s). Without such natal recruitment for at least the next 3-4 years, we should document a continuing decline in bird numbers at the colonies.

Alaska↗

USGS2022

Status and trends of the Lake Huron prey fish community, 1976-2019

The USGS Great Lakes Science Center has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October of each year and an acoustics-midwater trawl survey, which began in 2004 and is conducted in September-October. Both surveys were completed in their entirety in 2019. Prey fish biomass in Lake Huron in 2019 was dominated by two species, Bloater ( Coregonus hoyi ) and Rainbow Smelt ( Osmerus mordax ). In the main basin, prey fish biomass remained below levels observed prior to community-wide declines that began in the early to mid 1990s. Bloater was the most abundant prey fish species in the main basin, whereas Rainbow Smelt was the most abundant prey species in the North Channel and in Georgian Bay. Both surveys suggested that Bloater biomass is increasing in the main basin. Low biomass of invasive species like Alewife ( Alosa pseudoharengus ) and Rainbow Smelt is consistent with fish community objectives focused on restoration of native fish communities. Abundance of invasive Round Goby (Neogobius melanostomus) in 2019 was low relative to 2018. Biomass of the native Cisco ( Coregonus artedi ) continued to increase in the North Channel and Georgian Bay. Biomass of slimy sculpin ( Cottus cognatus ) and Deepwater Sculpin ( Myoxocephalus thompsoni ) in 2019 was down from 2018 but within the range observed over the past decade. Reduced lake productivity, predation by a recovering piscivore community, and shifts in food web dynamics that favor fish production in nearshore environments may prevent prey fish biomass in offshore areas from returning to levels observed prior to the early 1990’s. However, increased biomass of Bloater and Cisco suggests that lake conditions may favor recovery of native coregonids.

Lake Huron↗

USGS2022

Status and trends of the Lake Huron prey fish community, 1976-2020

The USGS Great Lakes Science Center (GLSC) has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October and an acoustics-midwater trawl survey conducted in September-October. In 2020, USGS-GLSC vessels were not permitted to cross into Canada due to the COVID-19 pandemic, so prey fish surveys sampled only sites in U.S. (Michigan) waters of Lake Huron. This prevented USGS from providing information about the current status and trends of prey fish communities in Georgian Bay and the North Channel. Prey fish biomass in U.S. waters of Lake Huron in 2020 remained below levels observed prior to community-wide declines that began in the early to mid-1990s. Fish community biomass was dominated by two species, Bloater (Coregonus hoyi) and Rainbow Smelt (Osmerus mordax). While both surveys found Bloater biomass in the main basin had declined from levels observed in 2019, Bloater still comprised over three-quarters of prey fish biomass in Lake Huron in 2020. Biomass and abundance for other prey fish species were within the range observed over the past five years. Current low biomass of invasive species like Alewife (Alosa pseudoharengus) and Rainbow Smelt is consistent with fish community objectives focused on restoration of native fish communities. Reduced lake productivity, predation by a recovering piscivore community, and shifts in food web dynamics that favor fish production in nearshore environments may prevent prey fish biomass in offshore areas from returning to levels observed prior to the early 1990’s. However, the dominance of Bloater in bottom trawl catches and acoustic surveys suggests that current lake conditions are conducive to the recovery of some native species.

Lake Huron↗

USGS2021

Long-term epilimnetic temperature trends in Lake Mendota and Trout Lake, Wisconsin

Warming of lake surface waters has become a concern to limnologists and water managers because a ir temperatures, which directly affect near - surface water temperatures, are projected to increase in Wisconsin (WICCI 2011) as well as globally (IPCC 2018). This projected increase is in addition to the changes in air temperatures that have already occurred in recent decade s (WICCI 2011, NOAA 2017) . The deleterious effects of increased temperatures in lake surface waters have been extensively reviewed ( e.g., Blenckner 2005, Keller 2007, Adrian et al. 2009, George 2010 ) . Briefly , t he exceedance of thermal preferences or tolerances of aquatic biota can cause altered food webs and loss of biodiversity in lakes ( De Stasio et al. 199 6 , Chu et al. 2005, Graham and Harrod 2009, Woodward et al. 2010, Comte et al. 2013 ) . W armer surface water temperature s can result in stronger and longer thermal stratification in deep lakes ( Robertson and Ragotzkie 1990, Hondzo and Stefan 1993, Livingstone 2003, Butcher et al. 2015 ) . This process in turn can cause the duration and extent of hypolimnetic anoxia to increase, thus reducing hypolimnetic refugia needed for cold - and cool - water fish ( De Stasio et al. 1996 , Magnuson et al. 1997, Jeppesen et al. 2012 , Missaghi et al. 2017) . Longer duration of hypolimnetic anoxia can enhance eutrophic ation because of more internal loading of phosphorus from bottom sediments ( Blenckner et al. 2002, North et al. 2014 ) . Of parti cular concern, w armer water temperatures favor the growth of toxic cyanobacteria in eutrophic systems ( Paerl and Huisman 2008, Wagner and Adrian 2009, Kosten et al. 2012 ) . Another effect of warmer lake surface temperature s is increased evaporation that can result in lower water levels ( Spence et al. 2013, Gronewold and Stow 2014 ) .

Wisconsin↗

USGS2022

Dynamic abiotic habitat

The factors affecting an organism can be divided into two general classes, abiotic and biotic. Abiotic factors include features of the physical and chemical environment, such as climate, water movement, and many aspects of water quality. Biotic factors refer to those involving living organisms and their interactions, such as the organisms and processes in a food web. We also distinguish between dynamic and stationary abiotic factors. Stationary abiotic factors are fixed in the environment and include things like landscape features (e.g., bays, channels, and surface elevations) that change relatively slowly over time. Dynamic abiotic factors vary over time and space at various scales ranging from sub-daily (e.g., tidal direction and velocity) to annually (e.g., total water inflow and outflow).

California↗

USGS2023

Status and trends of the Lake Huron prey fish community, 1976-2021

The U.S. Geological Survey Great Lakes Science Center has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October of each year and an acoustics-midwater trawl survey, which began in 2004 and is conducted in September-October. Due to weather delays and continued travel restrictions during 2021, there were no bottom trawl samples off the port of Goderich, Ontario and two acoustic transects were cancelled in Georgian Bay. Prey fish biomass in Lake Huron in 2021 was dominated by two species, Bloater (Coregonus hoyi) and Rainbow Smelt (Osmerus mordax). In the main basin, prey fish biomass remained below levels observed prior to community-wide declines that began in the early to mid 1990s. Bloater was the most abundant prey fish species in the main basin, whereas Rainbow Smelt was the most abundant prey species in the North Channel and in Georgian Bay. Both surveys suggested that Bloater biomass is increasing in the main basin. Low biomass of invasive species like Alewife (Alosa pseudoharengus) and Rainbow Smelt is consistent with fish community objectives focused on restoration of native fish communities. Abundance of invasive Round Goby (Neogobius melanostomus) increased in 2021 relative to 2019-2020. Biomass of the native Cisco (Coregonus artedi) increased in the North Channel in 2021 but remained low in Georgian Bay, possibly as an artifact of reduced sampling. Biomass of Slimy Sculpin (Cottus cognatus) and Deepwater Sculpin (Myoxocephalus thompsoni) in 2021 remained low but within the range observed over the past decade. Reduced lake productivity, predation by a recovering piscivore community, and shifts in food web dynamics that favor fish production in nearshore environments may prevent prey fish biomass in offshore areas from returning to levels observed prior to the early 1990s. However, increased biomass of Bloater and Cisco suggests that lake conditions may favor recovery of native corgonines.

Lake Huron↗

USGS2022

Floodplains and climate change

Floodplains are landscape features that are periodically inundated by water from adjacent rivers (Opperman et al. 2010). Ecologically, functional floodplains are characterized by three primary elements: connectivity, flow regime, and spatial scale. Water quantity flowing over floodplains can vary greatly. Based on a flood’s effects on the floodplain, three flood categories have been defined: floodplain-activation floods, floodplain-maintenance floods, and floodplainresetting floods (Box 1). Several physical parameters determine the types of ecosystems on floodplains and the species they will support; these include temperature, water depth, water velocity, and hydrologic connectivity (Opperman et al. 2010). Natural ecosystems commonly found on floodplains include annual vegetation, forests, seasonal wetlands, and permanent ponds or wetlands (Whipple et al. 2012). Floodplains provide many valuable ecosystem services: attenuation of flood flows which reduces flood risk, filtration of surface water, recreation, fisheries, agriculture, biodiversity, food availability, and groundwater recharge, which contributes to more-sustained and cooler dry-season flows (Opperman et al. 2010). -------------------------------------------------------------------------------------------------------------- Box 1 Floodplain-activation flood A small magnitude flood that occurs relatively frequently and produces characteristic ecological benefits such as food-web productivity and habitat creation for native fish spawning and rearing. Floodplain-maintenance flood A higher magnitude flood that, in addition to providing ecological benefits, results in geomorphic changes including bank erosion and deposition on the floodplain. Floodplain-resetting flood A very high-magnitude flood that occurs rarely and results in extensive geomorphic changes, such as the scouring of floodplain surfaces and changes in channel location due to avulsion. ----------------------------------------------------------------------------

California↗

USGS2022

Biology: Integrating core to essential variables (Bio-ICE) task team report for marine mammals

Marine mammals are wide-ranging, relatively long-lived organisms that play a crucial role in maintaining healthy ocean ecosystems. Often referred to as ecosystem engineers and sentinel species in marine ecosystems, these charismatic megafauna feed at a variety of trophic levels, affecting food web dynamics and cycling of chemicals and nutrients in the water column as well as in benthic habitats, both nearshore and in the deep ocean. An understanding of their abundance and distribution is an essential starting point for evaluating their role in ocean ecosystems. Accordingly, marine mammals have been included among key variables to monitor in ocean observing systems, from core variables for the U.S. Integrated Ocean Observing System (IOOS) to an Essential Ocean Variable (EOV) for the Global Ocean Observing System (GOOS). They also contribute to several Essential Biodiversity Variables (EBVs) for the Group on Earth Observations Biodiversity Observation Network (GEO BON). Further, evaluation of the health of marine mammal populations will help deliver societal benefits by contributing to the UN Decade of Ocean Science for Sustainable Development; informing reporting activities such as the World Ocean Assessment; and supporting achievement of Sustainable Development Goal 14, the post-2020 framework for the Convention for Biological Diversity, and a new treaty for conservation and sustainable use of marine biodiversity beyond national jurisdiction. In the U.S., the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (FWS) are required to produce stock assessments for marine mammals under the Marine Mammal Protection Act (MMPA, 16 U.S.C. §1371 et seq.). Stock assessment analyses require accurate, up to-date information on abundance and distribution to inform appropriate management and/or conservation measures. Despite the availability of information on abundance and distribution within the stock assessment reports, availability and accessibility of the underlying data to the broader ocean observing community and contribution to EOVs remain inconsistent.

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USGS2023

2023 Coastal master plan: ICM-wetlands – Submerged aquatic vegetation (SAV) updates

Submerged aquatic vegetation (SAV) provides critical structural habitat for valuable nekton and wildlife species across coastal ecosystems and can buffer the negative effects of land loss. Landscape change and restoration efforts across coastal Louisiana can impact the occurrence, coverage, and species assemblages of SAV, and changes to these foundational species can have cascading impacts across food webs. To support the 2023 Coastal Master Plan efforts, a unique SAV model was developed to assess coverage and occurrence of SAV across aquatic waterbodies in response to environmental variables evaluated. This effort created a spatial model describing the probability of presence of SAV across the study area in response to changing conditions over the modeled time period. To develop the initial coverage data layer, we used remotely sensed Normalized Difference Vegetation Index (NDVI) and modified Normalized Difference Water Index (mNDWI) data from 2015-2018 to identify areas containing variable vegetation and water spectral reflectance. Key environmental variables evaluated included total suspended sediments (TSS), salinity, and physical exposure. Seasonal estimates for TSS and salinity were used, as research indicates that seasonal environmental variability is a significant driver for SAV establishment. Seasonal salinity was derived from Coast-wide Reference Monitoring Station (CRMS) data, and seasonal TSS was estimated from hyperspectral imagery. Estimates of physical exposure have previously been provided by calculating fetch (the distance across water over which waves can propagate), but this proved to be too computationally intensive to be feasible, and we found distance to land to be a reasonable proxy for exposure. To represent geographic conditions and historical factors influences on SAV establishment and occurrence (e.g., variables too numerous and complex to model) we developed a basin variable that served as a proxy for complex historical, or prior, conditions, determined by the forested, fresh, intermediate, brackish, or saline (FFIBS) score. The final model included spring TSS, spring salinity, distance to land, and the basin prior. The model performed well for the area evaluated, correctly classifying SAV (as present or absent) 89% of the time (Kappa = 580). SAV probability of presence responded as expected to change in these environmental variables, with likelihood of occurrence decreasing in response to increasing spring TSS, spring salinity, and distance to land. However, the model was more accurate at predicting absence (true negative = 0.940) than predicting presence (true positive = 0.626), suggesting that the scale of the model may limit the ability to predict presence. Moreover, the simplicity of the model limited the accuracy in highly dynamic environments, for example near the outflow of diversions or areas of significant changes in salinity or TSS. Through incorporating underwater communities like SAV, this master plan provides a holistic view of coastal change and restoration. To create healthy ecological structure and function in wetland habitats, the submergent communities must be considered alongside the emergent habitats. As the benefits of SAV are increasingly recognized, both here in Louisiana and beyond, SAV restoration and the use of SAV communities in assessing and improving ecological condition are becoming more common.

Louisiana↗