Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / A summary of the sex hormones found in the various animal phyla is given. The phylogenetic implications of steroid presence and mode of reproduction are discussed particularly in regard to the evolution to viviparity. By paper and gas chromatographic methods, the gonads of the male Pecten were analyzed for androgens. None of the standard hormones could be identified, but a steroid compound of unknown identity was suggested by the experimental evidence. / 2031-01-01

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Studies were undertaken to examine the roles of iron and carbon in modulating prokaryotic growth in the ocean. The context of the first study was an open-open iron fertilization experiment in the high nutrient, low chlorophyll (HNLC) regime in the Southern Ocean. The context of the second study was the oligotrophic, iron-replete, and organic carbon-limited northwest Sargasso Sea. Experimental sea water cultures were amended with an iron chelator, desferrioxamine B (DFOB), and other nutrients to examine the effects of iron and carbon limitation on growth. In the first study prokaryotic abundance, carbon production, and growth rate increased in response to iron in two experimental locations north and south of the Antarctic Polar Front Zone (North Patch and South Patch, respectively). However, prokaryotes responded indirectly to iron-induced phytoplankton production. Prokaryotic production was highly correlated to particulate primary production (r2 = 0.80). Prokaryotes comprised a larger percentage of particulate organic carbon (POC) in the North versus the South Patch relative to non-fertilized waters. Analysis of prokaryotic community structure was also examined. Results showed unique prokaryotic communities existed in the North and South Patch for both iron-fertilized and non-fertilized waters. Additionally, community composition shifted over time in the South Patch and was distinct from non-fertilized waters. Measures of community diversity indicated an increase in taxonomic richness and diversity in iron-fertilized waters over time. Specific taxonomic groups monitored over time in the South Patch exhibited a differential response to the iron-induced phytoplankton bloom. at the domain level, the biomass response was greater for Eubacteria compared to Archaea. at the clade level, Cytophaga-Flavobacteria net biomass yields outpaced SAR11, although both exhibited significant increases (p < 0.05) in net growth rate over time in the South Patch. In the second study DFOB did not limit utilization of organic carbon (glucose). Conversely, DFOB stimulated prokaryotic growth in a dose-dependent manner. The trend of the response to DFOB was similar to glucose; however, the magnitude of the response (i.e. growth rate and biomass yield) at higher equivalent carbon doses was greater than that of glucose. Additionally, DFOB and glucose elicited a differential taxonomic response.

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Copepods are the dominant mesozooplankton in the Southern Ocean, but long- term change in their abundance and distribution along the Western Antarctic Peninsula (WAP), a region experiencing rapid climate warming, is unknown. Copepods are also potentially important grazers of phytoplankton in the WAP and contributors to carbon export through production of sinking fecal pellets. I examined summer (January- February) copepod community structure and abundance along the WAP over two decades (1993-2013) and investigated long-term trends in copepod abundance and their relationship with environmental parameters (sea ice, phytoplankton biomass and productivity, climate indices, and sea surface temperature). Copepods comprised on average 81% of total mesozooplankton abundance in the WAP; the copepod community was dominated by a few species that included Metridia gerlachei, Oithonaspp., and Calanoides acutus. There was a significant long-term increase in total copepod abundance over time, with higher abundances in years with earlier sea ice retreat and higher phytoplankton biomass and productivity. Trends for individual species reflected feeding and life cycle strategies, but generally followed those of total copepods. to examine the impact of copepod grazing on phytoplankton and contribution to carbon export, I conducted grazing and fecal pellet production experiments with the large dominant copepods (Calanus propinquus,Rhincalanus gigas, and C. acutus) in the WAP each January from 2012 to 2014. Copepods have a lowoverall impact on grazing of phytoplankton biomass (<1%) and productivity (1%, up to 11%). Copepods were likely feeding on other sources of carbon (i.e., protozoans and metazoans) besides phytoplankton to meet metabolic demands, especially in the offshore, slope region and in low chlorophyll a conditions. Fecal pellet production (egestion) rates were high, ranging from 0.82 (R. gigas)to 37.3μC ind. day -1 (Paraeuchaeta antarctica), and did not exhibit regional trends. My results suggest mechanisms leading to interannual variability of summer copepod abundance and grazing in the WAP can be used to predict how copepods will respond to future environmental changes and may affect the flow of carbon through the food web and the export of carbon to depth.