SEMINAR: Re: SPECIAL STUDENT SEMINAR MBF602--TODAY @ 1PM --TWO SPEAKERS

[Pam Harris <pharris@rsmas.miami.edu>]

MBF Student Seminar Series

Adam Greer

Advisor: Dr. Robert Cowen

“Small Scale Changes in Zooplankton Community during Upwelling and Relaxation Events in Monterey Bay, CA.”

Gelatinous zooplankton represent a poorly understood component of marine food webs in part because of difficulties estimating abundance using traditional net sampling techniques. The degree of vertical patchiness can influence the trophic impact of jellies, and the biophysical drivers of their distributions remain unknown. Using a towed In Situ Ichthyoplankton Imaging System (ISIIS), we examined the changes in jelly distributions during upwelling and relaxation events in Monterey Bay, CA. Sampling began at the end of a 12 day stretch of upwelling favorable winds. The first day of sampling was marked by a thin layer of high chlorophyll fluorescence and intense water column density stratification, with jellies, including large (> 8 cm bell diameter) scyphomedusae, most abundant at the strong vertical density gradient. Subsequent sampling days were characterized by decreasing chlorophyll fluorescence and reduced water column density stratification, along with increasing abundance of Pleurobrachia spp. and the hydromedusa Eutonina indicans. Surface-associated thin layers of copepods occurred after the relaxation event. These layers were surprisingly devoid of gelatinous zooplankton and did not overlap spatially with the subsurface thin chlorophyll layer, which suggests that thin layers may not represent zones of increased feeding.

 Alyson Venti/MAC

Advisors: Dr. David Kadko and Dr. Chris Langdon

“A Multi Tracer Model Approach to Estimate Reef Water Residence Times”

 Assessment of net ecosystem calcification (NEC) rates on coral reefs is critical to evaluate the response of these systems to ongoing ocean acidification. We present a novel approach based on distributions of ⁷Be and ²³⁴Th to estimate reef water residence times, a required parameter for estimating NEC rates but one that has historically been difficult to quantify. These tracers were applied to a time dependent model to estimate reef water residence times of the Bermuda reef system. The model was generated from biannual seasonal data collected between 2008 and 2010 at four sites across the Bermuda reef platform. Model results yielded residence times ranging from 1.4 (± 0.1) days at the rim reef to 11 (± 0.6) days closer to shore. These results agreed with previous estimates obtained with a regional physical circulation model. When incorporated with the alkalinity anomaly method these residence times yielded seasonal differences in NEC rates with platform average rates ranging from 20.3 (± 1.1) mmolCaCO₃ m^-2 d^-1 in November 2008 to 2.5 (± 0.1) mmol CaCO₃ m^-2 d^-1 in February 2009. These results are comparable to NEC rates estimated by scaling up calcification rates measured from individual corals. This novel approach for estimating NEC rates may be applicable to other energetic reef ecosystems, providing an opportunity to assess how these rates may change in the context of ocean acidification.

 

Friday, November 4, 2011

1:00pm

RSMAS campus, S/A 103