What happens to the critters in a hurricane?

Hurricane Irma – CNN image

Hurricanes are no fun! But, if there is a small silver lining to hurricanes, it’s that scientists are provided rare opportunities to gain new insights into some plant and animal species. It’s a field called disturbance ecology, and I suspect a lot of it will be taking place in the next few months to years.

Some insights from past disturbance are incredibly fascinating. For instance, in 2001, just prior to Tropical Storm Gabrielle’s landfall, 14 tagged blacktip sharks swam to deeper waters in Terra Ceia Bay. And, as Hurricane Charley approached Charlotte Harbor in 2004, six of eight tagged sharks moved to open water; the other two disappeared from the sampling array. In both cases, the timing of shark movement seemed to correspond to decreasing air and water pressure.

Another notable effect of Hurricane Charley, occurred in the Peace River and upper Charlotte Harbor, which went hypoxic (very low to no oxygen) following the storm’s passage. The hypoxia resulted in changes in fish assemblages, from our typical fish variety to only the hardiest, including the sailfin catfish and the invasive brown hoplo. The hypoxic event was short lasting, and the fish assemblages returned to normal within a month. Interestingly, the Myakka River, which did not see the eye of the storm was not affected by hypoxia or changes in fish assemblages.

Over on the east coast after Frances and Jeanne in 2004, scientists found that the estuarine fish within the Indian River Lagoon were more resistant to the inflow of freshwater than was estuarine fish in the St. Sebastian River. Scientists found the St. Sebastian River changed from its normal stratified system to a freshwater system for several weeks after the passage of the last hurricane. This was reflected in the loss of estuarine fish and an increase in freshwater fish species.

In the Caloosahatchee River, scientists have documented rapid downriver movements by juvenile smalltooth sawfish right after a tropical storm and freshwater pulse, an indication that these animals are affected by salinity, but can also quickly respond to changing conditions.

Where large, fast moving fish and marine mammals seem to be minimally effected by hurricanes as they can quickly leave the area or go deeper; slower moving fish, crabs, sea turtles, oysters, etc. are often much more significantly affected due to sudden reductions in dissolved oxygen, rapid salinity changes, and violent surf conditions. When large numbers of slower moving organisms are impacted, it can have long lasting effects on the overall community structure.

Habitats can also experience long lasting impacts. For example, 80% of the fringing mangroves around Charlotte Harbor were destroyed after Hurricane Charley in 2004. In 2007, a restoration project undertaken by scientists and anglers involved planting and dispersing mangrove propagules (the long seed pods) in upper Charlotte Harbor. From that project, we learn that in areas where natural recruitment is limited, due to a lack of healthy reproducing trees, we can jump-start recovery by simply adding healthy propagules. But mangroves grow very slowly and we are still experiencing recovery 13 years later.

A study published in 2006, found that loss of the fringing mangrove habitat and the shade cover it provided resulted in immediate changes in fish utilization of these areas. This study found that the most abundant small-bodied fish present after Hurricane Charley, were those that preferred non-vegetated bottom, such as lizardfish and spot. Less abundant species were those associated with seagrass or shore vegetation, including pinfish and pipefish. Some fish may have moved deep into the damaged shorelines to avoid predation and take advantage of the defoliated mangrove based food, but gear limitations would have prevented scientist from sampling these areas.

In the same study as above, seine data from 1996-2004 was compared from Tampa Bay and Charlotte Harbor. The scientists concluded that although the 2004 hurricane season affected some of the fish assemblages of Tampa Bay and Charlotte Harbor, these assemblages generally appeared quite resilient to natural environmental disturbances from a long-term perspective. Similar findings have been found locally for large bodied fish as well.

Sometimes scientists get lucky with fish already tagged and gear already collecting data when a storm approaches. Currently in Charlotte Harbor, gear is in the water in the Peace, Myakka, and Caloosahatchee rivers, and down around Pirate Harbor on the east wall. A good number of sawfish are tagged, some redfish are tagged, and a few goliath groupers are tagged. There may be other species I’m not aware of too. Many fish are tagged and being tracked in other Florida locations as well. What will we learn in the coming months or years? Time will tell; stay tuned.

 

Sources:

Greenwood, MFD, PW Stevens and RE Matheson Jr. 2006. Effects of the 2004 hurricanes on the fish assemblages in two proximate southwest Florida estuaries: Change in the context of interannual variability, Estuaries and Coasts, 29(6) 985-996.

Greenwood, MFD, CF Idelberger and PW Stevens. 2007. Habitat associations of large-bodied mangrove-shoreline fishes in a southwest florida estuary and the effects of hurricane damage, bulletin of marine science 80(3): 805–821.

Heupel, MR, CA Simpfendorfer and RE Hueter. 2003. Running before the storm: blacktip sharks respond to falling barometric pressure associated with Tropical Storm Gabrielle, Journal of Fish Biology 63: 1357-1363.

McNoldly, B. October 22, 2010. What happens underwater during a hurricane? UM, Rosenstiel School of Marine and Atmospheric Science. http://www.rsmas.miami.edu/blog/2012/10/22/what-happens-underwater-during-a-hurricane/

Paperno, R, DM Tremain, DH Adams, AP Sebastian, JT Sauer and J Dutka-Gianelli. 2006. The disruption and recovery of fish communities in the Indian River Lagoon, Florida, following two hurricanes in 2004, Estuaries and Coasts 29(6) 1004-1010.

Poulakis, GR, PW Stevens, AA Timmers, CJ Stafford and CA Simpfendorfer. 2013. Movements of juvenile endangered smalltooth sawfish, Pristis pectinate, in an estuarine river system: use of non-main-stem river habitats and lagged responses to freshwater inflow-related changes, Environ Biol Fish 96: 763-778.

Staugler, EA. 2011. Post-hurricane restoration of a red mangrove shoreline in the Charlotte Harbor Estuary, Florida: evaluating restoration techniques, FGCU 56 pp.

Stevens, PW, DA Blewett and JP Casey. 2006. Short-term effects of a low dissolved oxygen event on estuarine fish assemblages following the passage of Hurricane Charley, Estuaries and Coasts 29(6) 997-1003.

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