How does rising atmospheric CO2 affect marine organisms?

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Ecological Impacts of Poleward-Shifting Marine Species
Paper Reviewed
Gericke, R.L., Heck Jr., K.L. and Fodrie, F.J. 2014. Interactions between northern-shifting tropical species and native species in the northern Gulf of Mexico. Estuaries and Coasts 37: 952-961.

According to Gericke et al. (2014), "niche models applied in the context of future climate change predict that as regional temperatures increase, the distribution of tropical species will shift poleward." But they say that while such range expansions have been documented for a number of species, there is limited information on the ecological impacts such shifts may have on the native species into whose ranges they intrude.

Hoping to expand what is known about the subject, while noting that "abundances of tropically-associated gray snapper (Lutjanus griseus) and land snapper (Lutjanus synagris) have increased in seagrass nurseries in the northern Gulf of Mexico (GOM), concurrent with regional increases in sea surface temperature," Gericke et al. say they "investigated effects of increased abundances of these species on abundance and growth of pinfish (Lagodon rhomboides), the dominant native species," noting that "juvenile pinfish and snappers share common prey, predators and habitat," and that this "high degree of niche overlap suggests an equally high potential for competition."

More specifically, in the words of the three researchers, they say they employed "a multiple before-after control impact design to determine whether increased snapper abundances significantly affected abundance or growth of pinfish." This they accomplished by means of trawl surveys conducted at six locations in the northern GOM in the summer and fall of 2010, three of which locations had no snapper inhabitants and three of which had high snapper abundances, and by comparing pinfish abundance and otolith-determined growth rates at these locations that were representative of before and after snapper recruitment conditions. So what did they learn?

Gericke et al. report that "paired t tests and two-way analysis of variance revealed no significant differences in pinfish abundance or growth in the presence of snappers compared to locations and seasons without snappers." And they thus concluded that to that point in time (2010) "range expansions of tropically associated snappers have had no significant effect on abundance or growth of native pinfish in northern GOM seagrass habitats."

Reviewed 17 September 2014