Long Island Sound Sentinel Monitoring for Climate Change Program
Appendix B. Scope of Regional Climate Related Changes in the Long Island Sound Area
This section qualitatively characterizes the type, relative magnitude, and degree of uncertainty of key predicted changes in climate to LIS and its estuarine and coastal ecosystems and summarizes how those changes may interact with non-climate stressors. Many of the projected impacts described here apply to similar estuarine habitats along the Northeast (NECIA, 2006). Wherever possible, this section focuses on local impacts, however, as described in both published and unpublished documents and online sources concerning the Long Island Sound watershed (Figure 1). A number of significant climate changes have been observed within the Long Island Sound watershed over recent decades, and are projected to continue for the foreseeable future. While climate change is global in scale, as detailed in the Intergovernmental Panel on Climate Change
(IPCC) 2007 Synthesis Report (the Fourth Assessment Report, known as AR4; IPCC, 2007), the magnitude and type of expected changes vary regionally (GCRP, 2009; NECIA, 2006). Sea-level rise, for example, could be more rapid and pronounced along regional coastlines in the Northeast (defined here and after as the states of New Jersey and Pennsylvania, northward; Yin et al., 2009; GCRP, 2009).
The following sections summarize information on:
- Uncertainties associated with climate change predictions;
- Projected local and regional changes in climate, including projected changes in air temperatures; the amount and timing of precipitation and storm climatology; the rate and amount of sea-level rise; and changes in ocean conditions;
- Implications for existing stressors; and
- Risks to the Sound’s ecosystems.
i. Assessing Magnitudes of Change and Degrees of Uncertainty
The climate of the Earth is extremely sensitive. Small changes in various physical processes that control climate may lead to large-scale results. Some feedback loops are poorly understood, such as how climate change affects clouds and cloud cover, and many are difficult to model. So the climate’s propensity to amplify any small change makes predicting how much and how fast the climate will change inherently difficult. In addition, scientists have identified climatic tipping points - the point in which the global climate changes irreversibly from one state to a new state. Examples of tipping points include boreal forest dieback, loss of Arctic and Antarctic sea ice and melting of Greenland and Antarctic ice sheets, and disruption of the Indian and West African monsoons (Lenton et al. 2008). Therefore, there will always be some level of uncertainty with regard to the magnitude of predicted changes in climate as uncertainty is a fundamental characteristic of weather, seasonal climate, and hydrological prediction.
Uncertainty is an overarching term that refers to the condition whereby the state of a system cannot be known unambiguously. The degree of uncertainty varies for different climatic variables (e.g., temperature, precipitation, sea level rise) and the degree of change will vary with geographic location. For example, while IPCC AR4 (2007) expresses a high level of confidence in observed and predicted changes in global average temperature (for all emissions scenarios), sea level rise projections are more uncertain. While scientific observations indicate that global sea level rise is occurring and will continue to occur, the magnitude of future sea level rise will depend heavily on rates of Greenland and Antarctica ice sheet melt, changes in ocean circulation due to additional freshwater inflow (from melting ice), and naturally-cyclic hemispheric climate patterns. According to IPCC AR4 (2007), “[b]ecause understanding of some important effects driving sea level rise is too limited, [the AR4] report does not assess the likelihood, nor provide a best estimate or an upper bound for sea level rise.” There is also a great deal of uncertainty regarding “the extent to which society resolves to reduce further emissions of heat trapping gases” (NECIA, 2006). It is certain that CO2 emissions will continue to rise for at least the next several decades regardless of future actions to reduce emissions (IPCC, 2007; Copenhagen Synthesis Report, 2009). Uncertainty is not formally addressed in this plan, as most of the cited papers do not discuss uncertainty in a manner that could be consistently presented across the study topics.
ii. Projected Changes in Climate Patterns of Connecticut and New York
1. Changes in Air Temperature
Globally, air temperature has increased an average of 1.5°F since 1970. In the
Northeastern U.S., the average annual temperature has increased considerably more, by as much as 4°F in winter averaged over the period 1970 to 2000 (NECIA 2006). The average increase in annual temperature per decade has been 0.14°F over the full period of record; however the rate of temperature increase has been accelerating, averaging 0.5°F per decade between 1970 and 2002. Under a high-emissions scenario (continued heavy reliance on fossil fuels), average temperatures in the Northeast by 2100 could increase 8-12°F above historical levels in winter and 6-14°F in summer. Under a low-emissions scenario (a shift away from fossil fuels) increases would be about half as much (NECIA,
The frequency of summer days with a high heat index (temperature, with wind and humidity as factors) is also projected to increase. There will be more days with high temperatures reaching 90+°F in many Northeastern cities. Projections indicate that
Hartford could see more than 30 days reaching 100+°F (NECIA, 2006). According to the
Northeast Climate Impact Assessment (NECIA), “the typical northeastern summer day is projected to feel 12 to 16°F warmer than it did on average between [the reference period] 1961 and 1990” (NECIA, 2006). NECIA’s analysis indicates that by the end of the century under a high emissions scenario, summers in the NYC Tri-State Region are likely to feel similar to South Carolina summers of today (NECIA, 2006).
2. Changes in Precipitation and Storm Climatology
a. Changes in Seasonal Precipitation
Over the last several decades, the Northeast has experienced measurable changes to precipitation patterns; changes in these patterns are expected to continue and are likely to accelerate during this century. The primary observed change in precipitation over the region is a marked increase in annual precipitation of 5 to 10 percent since the turn of the twentieth century. By 2100, the region could see an additional four inches of precipitation annually, compared to the 1961-1990 reference period (NECIA, 2006). The greatest increases are expected with winter precipitation, with projected changes of 11 to 16 percent by 2050 and 20 to 30 percent by 2100. Additionally, as air temperatures rise, the Northeast can expect a continuation of recent trends in the type of precipitation experienced during winter (i.e., less snow and more rain; NECIA, 2006).
b. Changes in the Climatology of Heavy Precipitation Events
In addition to changes in seasonal and annual average precipitation, heavy precipitation events are expected to continue late-twentieth century trends, increasing in both frequency and intensity. By 2050, the amount of precipitation for a “rainy day” event is expected to increase eight to nine percent, with an increase of 10 to 15 percent by 2100. The frequency of such events is also likely
to increase by as much as 13 percent by the end of the century. Kirshen et al.
(2008) suggest that the 100-year Northeastern coastal storm event (by the 2005 definition) will increase in frequency to every 70 years by 2050 and to every 50 years by 2100. Heavy winter storms are also projected to reach the Northeast (becoming “Nor’easters”) with increasing frequency (NECIA, 2006). A recent study (Spierre and Wake 2010) looked at trends in extreme precipitation events for the northeastern US from 1948 to 2007. Analysis of data found an increase in extreme precipitation events and in annual precipitation with both occurring mainly during the spring and fall.
iii. Projected Changes in Long Island Sound and the Larger Northeastern Region of the
1. Sea Level Rise
Among the impacts of climate change are those projected to affect the world’s oceans.
Global sea level has been increasing due to thermal expansion of surface waters and increasing freshwater flow from melting glaciers and ice sheets at high latitudes. In the
last century, the planet has witnessed a sea level rise of eight inches, compared to almost
no rise for the previous 2,000 years (GCRP, 2009). The amount of sea level rise varies depending on local conditions, such as subsidence and uplift. Following retreat of the glaciers, coastal areas began to rebound from the removal of the tremendous weight of the ice. However, the earth’s crust warped due to the weight and present-day Connecticut was slightly uplifted. Following glacial retreat, Connecticut is subsiding at a rate of approximately 0.03 - 0.035 inches/year (0.76 - 0.89 mm/yr; Gornitz et al. 2004). An assessment of NOAA tidal gauge data (measuring relative sea level change) for New
London, CT, for 1938-2005, indicates that the average rate of sea level rise over that period was 0.08 inches/year (2.13 mm/yr; Kirshen et al., 2008). In Bridgeport, CT (1964 -
1999) and Montauk, NY (1947 - 1999) the relative sea level rise was 0.10 inches/year (2.54 mm/yr; Gornitz 2004).
The Intergovernmental Panel on Climate Change (IPCC) projects a global average sea level rise of up to two feet by 2100, even without accounting for the current break-up of
Greenland ice sheets (IPCC, 2007). Another recent study, also not accounting for recent ice sheet break-ups, indicates that global sea level could rise 2.0 to 4.5 feet by 2100, compared to the 2005 global average sea level (Frumhoff et al., 2007). A 2009 study projects that, when ice sheet melting and the associated changes in ocean currents are considered, coastlines of the Northeast could see an even greater rise in sea level compared to the global estimate. Boston and New York City, for example, could see a rise of 3.9 feet by the end of the century (Yin et al., 2009).
It should be noted that strong storm events exacerbate the threat of sea level rise. Kirshen et al.’s (2008) analysis indicates that in 100 years, during 100-year storm events, the maximum sea level at New London, CT could be about 10.2 feet (3.1 m) above base sea level. For comparison, the current maximum sea level height expected at New London during 100-year storm events is about 7.2 feet (2.2 m) above average sea level (Kirshen et al., 2008).
Several tools on projected sea level rise and storm surge impacts within the Long Island
Sound watershed is available. The Connecticut Department of Environmental Protection has a draft Connecticut coastal hazards website with a visualization tool that includes sea level rise: http://coastalhazards.uconn.edu/. Another tool focused on sea level rise impacts to salt marshes along the Connecticut coast was developed by Mark Hoover,
The Nature Conservancy and numerous partners have also developed a coastal resilience tool for Long Island, http://coastalresilience.org/. All tools have a goal of assisting with coastal planning and resource management.
2. Water Chemistry
While confounded by many factors such as depth and relatively rapid seasonal changes in water temperature, different currents, and limited data availability, there is general agreement that Long Island Sound (LIS) waters are increasing in temperature by approximately one degree Celsius (1.8 degrees Fahrenheit) every
100 years (O’Donnell 2010). This trend is resulting in profound impacts on biological communities such as fish and shellfish.
b. Acidity (pH)
Although the impact of increased atmospheric carbon dioxide (CO2) is most often linked to the warming of the atmosphere, it is also responsible for acidification of ocean waters. Ocean acidification occurs when CO2 dissolves in seawater, initiating a series of chemical reactions that increases the concentration of hydrogen ions and makes seawater more acidic, measured as a decline in pH. An important consequence of this change in ocean chemistry is that the excess hydrogen ions bind with carbonate ions, making the carbonate ions unavailable to marine organisms for forming the calcium carbonate minerals (mostly aragonite or calcite) that make up their shells, skeletons, and other hard parts (Doney et al., 2009; Pew Center, 2009).
Under preindustrial conditions, the atmospheric concentration of CO2 did not change over many millennia (Caldeira and Wickett 2003). However, as emissions have increased, there has been an accumulation of CO2 in the atmosphere and a net flux of CO2 from the atmosphere to the oceans. As a result, the pH of today’s ocean has declined in relation to the pre-industrial period by 0.1 pH unit (on a log scale), representing a 30-percent increase in ocean acidity (Caldeira and Wickett 2003). The pH and carbonate ion concentrations of the world’s oceans are now lower than at any time in at least the past 420,000 years (Hoegh-Guldberg et al. 2007). By 2100, depending on the emissions scenario modeled, the average ocean pH could decline by 0.3 to 0.5 pH units in relation to pre-industrial levels (Caldeira and Wickett 2005).
3. Projected Changes in Sea Floor Geochemistry
Directly tied to changes in LIS water chemistry are projected changes in sea floor geochemistry. Changes in water temperature and dissolved oxygen levels may lead to a reduction of oxygen in surface sediment as well as cause leaching of contaminants out of the surface sediments. Such changes have the potential to impact numerous organisms.
Data compilation, analysis and further data collection including food web impacts are a need for this subject area.
4. Projected Changes in Selected Ecosystems of Long Island Sound Biological
Communities and Processes of Long Island Sound
a. Coastal Barriers, Beaches, and Dunes
Headland erosion is the main process of beach development along the north shore of Long Island, creating narrow strips of beach below bluffs and steep cliffs. The
Connecticut shoreline overlays bedrock, making erosion much less likely (LISS
2003). Where beaches occur, beach retreat in response to sea level rise depends on the average slope of the beach profile. It is estimated that in the region from
Maine to Maryland, a one-meter rise in sea level would result in beach retreat of
50-100 m (Gornitz 2001). Sandy beaches not only serve as popular recreational areas, they also provide protection of nearby property against erosion from wind and coastal storm surges.
Beaches also provide habitat for a wide variety of species. The invertebrate infauna of the foreshore, between the highest and lowest tide zones, provides forage for migrating shorebirds. The maritime beach community between mean high tide and the primary dunes provides nesting sites for horseshoe crabs and several rare bird species, including piping plover, American oystercatcher, black skimmer, least tern, common tern, and roseate tern. This area also provides habitat for horseshoe crabs and the northeastern beach tiger beetle (thought to be extirpated in NY, but occurs in CT), which is federally listed as threatened. Dunes and the upper back barrier beach provide nesting habitat for diamondback terrapins (Strange 2008 and references therein).
b. Tidal Wetlands
The extraordinarily high primary production of tidal wetlands supports an extensive estuarine food web. Wetlands also filter sediments and contaminants; protect against erosion and flooding; and provide habitat for both aquatic and terrestrial wildlife (Teal 1986; Mitsch and Gosselink 2003).
Tidal wetlands are an important coastal habitat in Connecticut, but are a relatively uncommon along the north shore of Long Island because of the area’s steep uplands and sea cliffs. Most salt marshes are found in embayments, such as
Mount Sinai and the three large bays of western Long Island Sound (Little Neck
Bay, Manhasset Bay, and Hempstead Harbor; NYDEC, 2004), as well as along numerous coves and embayments along the Connecticut coast.
Tidal wetlands can respond to sea-level rise in a number of ways depending on local elevation, geomorphology, and land use. As seas rise, tidal wetlands can migrate inland if not impeded by geological features or human-made barriers, such as seawalls and roads, and if the rate of migration exceeds the rate of erosion at the seaward edge. Wetlands that are unable to accrete sufficient sediment to keep pace with sea level rise will become increasingly flooded and will eventually convert to open water or tidal flat. High marsh may convert to low marsh and, in situations where the coastal plain is not obstructed, upland habitat may convert to salt marsh. There may also be changes in the relative abundance of marsh vegetation, with increases in the invasive Phragmites australis, which tolerates lower salinity. Over the past few decades, local scientists have noted marsh submergence in some areas, and emergent marsh (particularly low marsh) is converting to tidal flats along many of the tidal rivers draining to the Sound (Ron Rozsa, unpublished observations). A sea-level rise of up to 4 feet, projected for
the Northeast by Yin et al. (2009) during the 21st century, would make it less likely marshes will be able to fully compensate for the rise in sea level.
Salt marsh islands provide nesting sites for a number of bird species, particularly colonial nesting waterbirds. Gull-billed terns, common terns, American oystercatchers, and black skimmer commonly nest on marsh islands. Saltmarsh sparrows and seaside sparrows, both of which are very high conservation priorities in southern New England, nest in Connecticut salt marshes. Studies show that the submergence and erosion of marsh islands as a result of sea level rise are already affecting bird species that depend on these areas for protection from predators (Erwin et al., 2006).
c. Tidal Flats
Sediments eroded from bluffs along the north shore of Long Island are carried by longshore drift, primarily east to west, and later deposited to form tidal flats and shoals. Tidal flats provide invertebrate forage for waterbirds and habitat for shellfish such as clams. One of the largest areas of tidal flat in the Sound occurs near Conscience Bay, Little Bay, and Setauket Harbor, where there are large beds of hard clams, soft clams, American oysters, and ribbed mussels (NYSDCR, 2004).
The largest threat to the tidal flats of Long Island Sound is sea level rise. Initially, rising seas may convert low marsh to tidal flat, but eventually tidal flats will become entirely submerged, making the invertebrate infauna of the flats inaccessible to foraging waterfowl and shorebirds. Accessibility of invertebrate forage is directly tied to the ability of shorebirds to thrive (Nicholls et al., 2007).
d. Subtidal Zone
Subtidal habitats include nearshore benthic habitats of unconsolidated sediments (ranging in size from clays to gravel) and areas of submerged aquatic vegetation, mostly eelgrass. Eelgrass provides food, shelter, and nursery habitats for many economically-valuable species, including shellfish such as lobsters, scallops, clams, and mussels, and finfish such as Atlantic cod, Atlantic herring, and several varieties of flounder. Some bird species feed on eelgrass. Eelgrass was once common throughout the shallow coastal waters of Long Island Sound. Many of the eelgrass beds were lost due to a large scale die off in the 1930’s, but reestablished in eastern LIS by the 1950’s. Today eelgrass populations are impacted by pollution, with nitrogen loading thought to be particularly problematic.
Light is the primary factor affecting eelgrass distribution and abundance. As sea levels rise, these remaining seagrass beds may fail to thrive because of reduced light penetration. Short and Neckles (1999) predicted that a 50 cm (19.7 in) increase in water depth as a result of sea level rise, which could occur by 2100, would reduce the light available for seagrass photosynthesis by 50 percent, resulting in a 30-40 percent decline in seagrass growth worldwide. The movement of eelgrass beds shoreward as sea levels rise could be impeded in areas with steep shores or where there is erosion and water turbidity in front of shoreline protection structures such as seawalls and bulkheads. Rising water temperatures also pose a problem for eelgrass, which becomes stressed if water temperatures exceed 86° Fahrenheit for extended periods (Orth and Moore,1986; Moore and Jarvis 2008).
Benthic animals such as molluscs (e.g., clams) and crustaceans (e.g., lobsters) may also fail to thrive as waters warm. However, soft clams (Mya arenaria), which require temperatures near 32° C (Kennedy and Mihursky, 1971 cited in Pyke et al., 2008), may increase in relative abundance as waters warm. There is also evidence that warmer waters may enhance production of blue crab in Long Island Sound (Fogarty et al., 2007).
e. Open Waters
The plankton and finfish of the Sound’s open waters are vulnerable to a number of changes in physio-chemical conditions that are expected to result from climate change. Open water species may experience adverse effects with increases in water temperatures, lower dissolved oxygen as waters warm, and increased nutrient loadings from increased runoff and freshwater inflow resulting from an increase in the frequency or intensity of heavy precipitation events. Plankton are an important food source for finfish. Larval fishes feed on zooplankton and their growth and survival can be reduced if the peak in zooplankton abundance does not coincide with the presence of fish larvae. Excessive phytoplankton blooms or changes in the timing of blooms, initiated by the timing of the spring freshet, can result in adverse effects on finfish and other open water species. If phytoplankton blooms do not occur when fish move inshore to spawn, larvae may lack sufficient zooplankton resources since zooplankton depend on the spring phytoplankton bloom. At the same time, excessive blooms, promoted by higher nutrient levels resulting from increased runoff, can deplete dissolved oxygen, harming both zooplankton and fishery species.
Ocean warming is already having a discernable effect on the a number of species in the region. Scientists have observed a shift from coldwater finfish species such as winter flounder to species found in warmer waters to the south (Wood et al.,
2009). In Narragansett Bay, warmer waters have led to an overlap in the presence
of early life stages of winter flounder and comb jellies (Mnemiopsis leidyi), which feed on winter flounder eggs and larvae, contributing to reductions in winter flounder populations (Sullivan et al., 2001).
f. Freshwater Tributaries
The Sound’s tributaries provide a number of ecological values that support resident and migrant species of the Sound. Important freshwater wetlands are found along the lower Connecticut River. The river was designated a Wetland of International Importance under the Ramsar Convention because it supports the best examples of fresh and brackish marshes and submerged aquatic vegetation (SAV) beds in the Northeastern U.S. Depending on the amount and timing of precipitation and freshwater flow in spring, these areas provide freshwater impoundments that are important for migrating birds (LISS, 2003). Freshwater wetlands may support greater bird diversity than any other wetland type (Mitsch and Gosselink, 2003). Freshwater inflow from the Sound’s tributaries, including the Connecticut, Housatonic, Thames, and Quinnipiac Rivers, helps determine surface water conditions in the estuary. Heavy precipitation events, expected to increase in severity and frequency over the coming decades, may periodically reduce the salinity of the waters of the Sound and increase nitrogen and sediment loadings. Low salinity can lead to localized die-offs of shellfish and finfish and, if prolonged, reduce the spatial extent of benthic habitats such as SAV seagrass beds. The Connecticut River watershed drains 11,000 square miles from the Canadian border south to Long Island Sound. While scientists have documented an increase in extreme precipitation events and in annual precipitation in the northeastern United States, these increases are occurring mainly in the spring and fall (Spierre and Wake, 2010). If less precipitation falls as snow within the watershed, then the annual spring freshet of the Connecticut River may be reduced. Predicted decreases in the volume of the spring freshet will inhibit ponding and the formation of natural freshwater impoundments, which are important for migrating waterfowl during the early spring. As sea-level rise raises salinity in tributaries, freshwater wetlands will convert to brackish marshes. Eventually only vegetation favored by high salinity will remain. Increases in storm intensity may accentuate marsh fragmentation. Increased runoff carries heavier loads of nutrients (such as nitrogen), pathogens, and harmful chemicals. Additional runoff could not only overwhelm the ability of tributary wetlands to filter these elements before entering LIS, but could also directly damage the health of animal and plant species in these habitats (Nicholls et al., 2007).
g. Fisheries of Long Island Sound and Associated River Systems
Temperature is only one of a complex group of variables that individually or collectively drives ecological changes in LIS. Subsequently, it is difficult to definitively attribute or project changes in crustaceans, mollusks, and finfish populations without considering other environmental influences. The net effect of increased temperature on fish (crustaceans, bivalves, finfish) populations may be negative or positive. It is foreseeable that synergies may exist between climate change and other major stressors. Generally, fish have the ability to actively migrate to avoid unfavorable conditions. However, if unfavorable conditions persist indefinitely, this creates an entirely new habitat that would have far reaching ecological consequences. In the case of marine species that are being exploited in LIS, the climate-related impacts would be a result of temperature, low dissolved oxygen, and reduced pH (acidification). The severity of these impacts may be different at various life stages. Climate change places additional pressure on exploited marine fish stocks that are already subject to over exploitation and other stressors (Harley et. al, 2006).
Talmage and Gobler (2009) studied the effects of reduced pH (ocean acidification) on the larvae of three bivalves – hard clam, bay scallop and Eastern oyster (Mercenaria mercenaria, Argopecten irradians, and Crassostrea virginica) – and observed significantly stunted growth and lower rates of metamorphosis. The ability of calcifying organisms to synthesize calcium carbonate shells could become seriously diminished and organisms that adapt and survive may have fragile shells that offer less protection from predators and pathogens. This sensitivity of the calcium carbonate shell towards ocean acidification is believed to be exacerbated in the larval stage. These effects would not be confined to wild fisheries, shellfish growers could be dealing with new challenges in the grow-out phase of production. Combined with the prognosis by Joos et al. (1999) that the ‘thinning effect’ will be more significant in states of higher altitudes and colder waters, these fisheries may become reduced or possibly even extinct in LIS. Furthermore, these projections could influence the success (or failure) of planned shellfish restoration efforts in LIS. If seeds do not have good survival rates, then it will be extremely difficult to rebuild the wild population.
i. American Lobster
The greatest concern for American lobster (Homarus americanus) populations may be the result of temperature regime shifts. American lobsters inhabit most of the eastern coast of North America from northern Labrador to North Carolina (Herrick, 1911). Presently, LIS represents the southern end of the inshore range (Stewart, 1972; Lawton and Lavalli, 1995). Tin (2005) suggests an average of four degree increase in global climate would move American lobster populations from the southern range to waters at higher latitudes. So called ‘climate change induced range shifts’ have been studied by other scientists (Chueng et al., 2009). American lobsters can acclimate and survive temperatures ranging from -1 ºC to 30.5 ºC (Lawton and Lavalli, 1995), with demonstrated thermal preference of about 16 ºC. Under unfavorable conditions, these animals actively migrate because they cannot control their own body temperature. Seasonal migration is important and the occurrence of a long term warming regime would result in a net loss of favorable habitat. Moreover, if American lobsters survive in unfavorable habitats, these populations may have seriously compromised neurological and metabolic functions (Worden et al., 2006). A noticeable absence of American lobsters from named habitats will have far-reaching impacts on the ecosystem, as well.
j. Marine Finfish
Finfish can actively avoid unfavorable conditions and several studies predict climate is most likely to force species ranges towards higher latitudes (Perry et al.,
2005). For marine fishes, distribution and abundance are being driven by temperature impacts on growth, spawning, and changes in food source. Perry et al. (2005) further concludes that latitude shifts will be accompanied by shifts in depth, which could create new challenges in fisheries. Given the high mobility, marine fish will shift their ranges more quickly than sedentary organisms, unless they are being confined by habitat or dispersal capability. If the marine fish species has a slower life history and is commercially viable, these populations may be unable to sustain the fishing pressures while adapting to climate driven range shifts (Perry et al., 2005). It may become necessary to change fishing operations.
Temperature affects the biology (i.e., growth, timing of spawning, quality of eggs) of marine finfish. Previous studies suggest large females are more likely to spawn earlier, which could prompt revisions to conservation plans. While studying the thermal dynamics of ovarian maturation in Atlantic cod (Gadus morhua), Kjesbu et al. (2010) observed females being held above the ambient temperature displayed improved appetite and invested more energy in growth. Although a better nutrition level enhances the condition indices and increased egg production (fecundity), trade-offs in other health factors are to be expected, such as impinged liver, and noticeably poorer egg quality. Compromised health of individuals could have an overall adverse effect on population dynamics (e.g., inadequate recruitment levels to sustain exploitation).
k. Diadromous Fish
Diadromous fish have been reported as keystone species in ecosystems by serving unique roles (referenced in Lassalle and Rochard, 2009). Striped bass populations in LIS spend a part of their life in the Chesapeake Bay, and a major loss in habitat foreseen in this estuary (Chesapeake) would have a domino effect on LIS populations (Lassalle and Rochard, 2009). Limburg and Waldman (2009) in their review attributes the loss of the boreal rainbow smelt (Osmerus mordax) in the Hudson River to a continuum of climate-driven range shifts; it is possible this species may no longer exist in waters south of Maine in the future. The gizzard shad (Dorosoma cepedianum) was also reported to be presently embarking upon a northward migration after establishing large populations in the Hudson River through Maine. Climate has been known to accelerate the spawn timing by more than a day for several diadromous prey fish, which may have severe trophic interaction implications. Jonsson, Jonsson, and Hansen (2005) discovered environmental conditions encountered early in the life cycle of Atlantic salmon do have an influence on their development. In fact, warm and mild winters promote growth in the first year, forcing young of the year to migrate from their river nurseries to the sea at a younger age. This type of biological consequence has been reported in other species, including sockeye salmon (Oncorhynchus nerka) that have been observed to arrive up to one month earlier before historical spawning, when river temperature was below 19°C (Hodgeson and Quinn, 2002 referenced in Jonsson, Jonsson, and Hansen, 2005). In general, climate plays a significant role in diadromous fish early development because egg incubation is improved in warmer temperature causing larvae to emerge earlier.
For citations listed above, see the References section.