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Updated: 28 min 29 sec ago

Hurricane Sandy Impacts Did Not Contribute to Subsequent Storm Flooding

Tue, 05/27/2014 - 11:00
Summary: Flooding in coastal areas bordering Great South Bay, N.Y. and Barnegat Bay, N.J. caused by winter storms that occurred following Hurricane Sandy was not influenced by changes Sandy made to barrier islands or other bay features, according to a new U.S. Geological Survey study Study looks at Great South Bay and Barnegat Bay

Contact Information:

Alfredo Aretxabaleta ( Phone: 508-457-2204 ); Bradford Butman ( Phone: 508-457-2212 ); Neil Ganju ( Phone: 508-457-2252 );

WOODS HOLE, Mass. —Flooding in coastal areas bordering Great South Bay, N.Y. and Barnegat Bay, N.J. caused by winter storms that occurred following Hurricane Sandy was not influenced by changes Sandy made to barrier islands or other bay features, according to a new U.S. Geological Survey study.

The study of Barnegat Bay and Great South Bay looked at data from November 2012 to October 2013, when winter storms brought water levels in these bays to among the 20 highest storm water levels reached from October 2007- October 2013.

“The frequent and extreme high-water levels caused by storms in these two bays in the months after Hurricane Sandy led to perceptions the mainland was more vulnerable to flooding,” said USGS oceanographer and coauthor of the study Neil Ganju. “This study shows that changes to bay features caused by Hurricane Sandy did not influence these post Sandy storm water levels.”

Hurricane Sandy caused extreme floods along portions of the northeast coast of the U.S. and cut new inlets across barrier islands in New Jersey and New York. Scientists investigated whether Hurricane Sandy had in some way reduced the protection provided by the barrier islands and the bays, leaving the mainland more vulnerable to flooding.

The study compared water level measurements made at stations within Great South Bay and Barnegat Bay to ocean water levels before and after Hurricane Sandy. Both are back barrier bays -- bodies of water behind barrier islands and connected to the ocean through one or more inlets.

“Changes in water levels in the back-barrier bays are primarily caused by ocean water levels driving water into or out of the bays through inlets,” said USGS oceanographer and lead author of the study Alfredo Aretxabaleta.  “The study showed that most of the ocean water level fluctuations caused by storms make their way into the bays, while only a fraction of tidal fluctuations do.”

The results showed that alterations to the barrier, inlet, and bay systems caused by Hurricane Sandy did not influence the high water levels caused by storms from November 2012 to October 2013. None of these post-Sandy storms opened new inlets or caused overtopping of the protective dunes and barrier beach systems. Both before and after Sandy, about 80 percent of storm surge—a temporary rise in water level caused by an offshore storm’s winds or low pressure—made its way into the back barrier bays, whereas only about 20 percent of the tidal fluctuations do. This suggests that whether the same storm occurred before or after Hurricane Sandy, the water level in the bays would be the same.   

“While the existing barrier island and inlet system shields the mainland to a great extent from the daily tides, most of the storm surge, and all long-term changes in water level, such as those resulting from sea level rise, reach the mainland” said USGS oceanographer and coauthor Bradford Butman. “These results will inform coastal communities and planners how water levels in back-barrier bays respond to ocean fluctuations.”

Several studies related to Hurricane Sandy recovery, restoration and rebuilding efforts, many of which are funded by Disaster Relief Appropriations Act 2013, are currently underway.

“The USGS is committed to providing the science foundation for federal, state, and local authorities to build more resilient communities,” said John Haines, coordinator of the USGS’ Coastal and Marine Geology Program. “This is one of many studies the USGS is doing to understand the effects of Hurricane Sandy and to evaluate the vulnerability of the coast and its communities to future storms.”

The study, “Water-level response in back-barrier bays unchanged following Hurricane Sandy,” by Aretxabaleta, A.L., Butman, B., and Ganju, N.K., is in the Geophysical Research Letters journal and available online.

Climate Change Accelerates Hybridization between Native and Invasive Species of Trout

Sun, 05/25/2014 - 12:00
Summary: Scientists have discovered that the rapid spread of hybridization between a native species and an invasive species of trout in the wild is strongly linked to changes in climate

Contact Information:

Suzanna Soileau ( Phone: 406-994-7257 ); Clint Muhlfeld ( Phone: 406-600-9686 );

BOZEMAN, Mont. – Scientists have discovered that the rapid spread of hybridization between a native species and an invasive species of trout in the wild is strongly linked to changes in climate.

In the study, stream temperature warming over the past several decades and decreases in spring flow over the same time period contributed to the spread of hybridization between native westslope cutthroat trout and introduced rainbow trout – the world’s most widely introduced invasive fish species –across the Flathead River system in Montana and British Columbia, Canada.

Experts have long predicted that climate change could decrease worldwide biodiversity through cross-breeding between invasive and native species, but this study is the first to directly and scientifically support this assumption. The study, published today in Nature Climate Change, was based on 30 years of research by scientists with the U.S. Geological Survey, University of Montana, and Montana Fish, Wildlife & Parks.

Hybridization has contributed to the decline and extinction of many native fishes worldwide, including all subspecies of cutthroat trout in western North America, which have enormous ecological and socioeconomic value.  The researchers used long-term genetic monitoring data coupled with high-resolution climate and stream temperature predictions to assess whether climate warming enhances interactions between native and nonnative species through hybridization.

“Climatic changes are threatening highly prized native trout as introduced rainbow trout continue to expand their range and hybridize with native populations through climate-induced ‘windows of opportunity,’ putting many populations and species at greater risk than previously thought,” said  project leader and USGS scientist Clint Muhlfeld. “The study illustrates that protecting genetic integrity and diversity of native species will be incredibly challenging when species are threatened with climate-induced invasive hybridization.”

Westslope cutthroat trout and rainbow trout both spawn in the spring and can produce fertile offspring when they interbreed. Over time, a mating population of native and non-native fish will result in only hybrid individuals with substantially reduced fitness because their genomes have been infiltrated by nonnative genes that are maladapted to the local environment. Thus, protecting and maintaining the genetic integrity of native species is important for a species’ ability to be resilient and better adapt to a rapidly changing climate.  

Historical genetic samples revealed that hybridization between the two fish species was largely confined to one downstream Flathead River population. However, the study noted, over the past 30 years, hybridization rapidly spread upstream, irreversibly reducing the genetic integrity of native westslope cutthroat trout populations. Genetically pure populations of westslope cutthroat trout are known to occupy less than 10 percent of their historical range.

The rapid increase in hybridization was highly associated with climatic changes in the region. From 1978 to 2008 the rate of warming nearly tripled in the Flathead basin, resulting in earlier spring runoff, lower spring flooding and flows, and warming summer stream temperatures. Those locations with the greatest changes in stream flow and temperature experienced the greatest increases in hybridization. 

Relative to cutthroat trout, rainbow trout prefer these climate-induced changes, and tolerate greater environmental disturbance. These conditions have likely enhanced rainbow trout spawning and population numbers, leading to massive expansion of hybridization with westslope cutthroat trout.

“The evolutionary consequences of climate change are one of our greatest areas of uncertainty because empirical data addressing this issue are extraordinarily rare; this study is a tremendous step forward in our understanding of how climate change can influence evolutionary process and ultimately species biodiversity,” said Ryan Kovach, a University of Montana study co-author.

Overall, aquatic ecosystems in western North America are predicted to experience increasingly earlier snowmelt in the spring, reduced late spring and summer flows, warmer and drier summers, and increased water temperatures – all of which spell increased hybridization between these species.

The article, published in Nature Climate Change, is titled “Invasive hybridization in a threatened species is accelerated by climate change” and can be viewed at the following website.  Its authors are Clint Muhlfeld, U.S. Geological Survey; Ryan Kovach, University of Montana; Leslie Jones, U.S. Geological Survey; Robert Al-Chokhachy, U.S. Geological Survey; Matthew Boyer, Montana Fish, Wildlife and Parks; Robb Leary, Montana Fish, Wildlife and Parks; Winsor Lowe, University of Montana; Gordon Luikart, University of Montana; and Fred Allendorf, University of Montana.

This study was supported by the Great Northern Landscape Conservation Cooperative, the Interior Department’s Northwest Climate Science Center, the National Climate Change and Wildlife Science Center, National Science Foundation, and Bonneville Power Administration.   

More information about impacts and prevention of invasive species and hybridization can be found on the USGS Northern Rocky Mountain Science Center website

Genetic Analysis Reveals Fish Eggs Found in Upper Mississippi River are not Asian Carp

Thu, 05/22/2014 - 14:00
Summary: Scientists have extracted DNA from fish eggs found in northern sections of the Upper Mississippi River and have determined that the eggs and larvae are not from Asian carp

Contact Information:

Dave Ozman ( Phone: 303-202-4744 ); Catherine Puckett ( Phone: 352-377-2469 );

Scientists have extracted DNA from fish eggs found in northern sections of the Upper Mississippi River and have determined that the eggs and larvae are not from Asian carp.  Genetic analysis instead shows that the fish eggs collected in the summer of 2013 likely belong to a native North American species in the same family as carp.  All Asian carp species are considered invasive species and belong to the cyprinid fish family.  

To confirm visual identification of the eggs’ species, scientists from the U.S. Geological Survey genetically tested 41 of the 65 eggs and larvae that were collected from the Upper Mississippi River (Pool 9 and Pool 11) in Wisconsin and Iowa.  DNA sequences successfully obtained from 17 eggs revealed that they were similar to those of other cyprinid fishes and did not come from Asian carp.  The one exception was an egg collected from Pool 19 in southern Iowa, which had been visually identified as an Asian carp, and was later genetically confirmed by the USGS as a grass carp, one of the four Asian carp species.  

“What we have learned from this research is that non-Asian carp cyprinid eggs in the northern portions of the Upper Mississippi can closely resemble Asian carp eggs in size and shape,”  said Leon Carl, USGS Midwest Region Director.  “These findings underscore the importance of using genetic testing to confirm the results of visual identification.” 

Researchers were surprised to learn that the large eggs from Pools 9 and 11 belonged to other species in the cyprinid family rather than to Asian carp species.  Such findings are contrary to previously published work that had established that non-Asian carp cyprinids indigenous to the Midwest have considerably smaller eggs compared to the invasive carp that were the focus of the study. 

Detailed visual analysis of the eggs’ size and shape earlier this year indicated that they were consistent with the eggs of Asian carp species and led scientists to believe that invasive carp may have successfully spawned in this northern portion of the Upper Mississippi.  Given the seriousness of the Asian carp spread northward, USGS scientists alerted partners and the general public about that potential in March and decided to pursue genetic testing to confirm the visual findings.

Scientists emphasized that the recent genetic data will modify their application of visual identification methods to distinguish fish eggs and larvae collected in the Upper Mississippi River. The difficulty USGS scientists had in genetically testing the eggs suggests that researchers and managers studying or monitoring Asian carp reproduction in North America should consider separately preserving, for genetic analysis, a subset of collected embryos to confirm visual identification. 

USGS researchers will continue efforts to gain a better understanding of how egg size, location of eggs within the river and flow conditions may help to identify those habitats important to reproduction of native and non-native cyprinids including Asian carp.  Understanding habitat requirements will assist in the development of methods to control invasive Asian carp.