Date of Award

8-31-2014

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Marine Sciences and Technology

First Advisor

Juanita Urban-Rich

Second Advisor

Pia H. Moisander

Third Advisor

Alan Christian

Abstract

Jellyfish are an important component of many coastal ecosystems and recent work has shown they can interact with microbial communities. Studies have shown that gelatinous and crustaceous zooplankton can not only release dissolved organic matter (DOM) that can alter the respiration and community structure of bacteria in the surrounding water, but also can harbor microbial communities that differ from the surrounding seawater. Such studies have not been conducted in Massachusetts waters with a Scyphomedusa (Aurelia aurita) and Hydromedusa (Nemopsis bachei). Nemopsis Bachei is a colonial coastal hydrozoan native to the East Coast of the United States, and within the past 20 years these hydrozoans have invaded the European waters of the Atlantic and German Bight. A. aurita is a cosmopolitan schyphozoa capable of producing large blooms in the Atlantic, Pacific, and Indian Oceans. This study furthers our knowledge on this gelatinous zooplankton by comparing DOC effects of hydrozoans against known results of scyphomedusa, both classes being of the Cnidarian phylum, as well as examining the microbial communities of two Cnidarians within Massachusetts coastal waters. Laboratory experiments show that N. bachei releases labile dissolved organic carbon (DOC) into the surrounding water such that bacterial abundance increases and the microbial community shifts. Using the molecular fingerprinting method of terminal restriction fragment length polymorphism (T-RFLP) it was found that Gammaproteobacteria and Bacteroidetes became more dominant in the bacterial community in response to N. bachei produced dissolved organic matter (DOM). Cloning and sequencing results from hydromedusa directly picked from the water support these trends. Both Nemopsis bachei and Aurelia aurita had significantly different bacterial communities than that of the surrounding seawater. N. bachei bacterial sequences were dominated by Gammaproteobacteria, Bacteroidetes, and Alphaproteobacteria whereas A. aurita was dominated by Cyanobacteria, Tenericutes, and bacteria that could not be classified. These cnidarian-associated bacteria are suggestive of symbiotic associations that could be of importance in nutrient cycling or potential pathogenic abilities.

Comments

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