SEMINAR: MGG Student Seminar: Tue April 20

[Monica Arienzo <marienzo@rsmas.miami.edu>]

**MGG STUDENT SEMINAR**

Third Floor CIMAS Conference Room
Tuesday, April 20

12:30 - 1:30 pm
NOTE TIME CHANGE!


SEDIMENT BIOFILMS: REFUGIA FOR FECAL INDICATOR BACTERIA AND OTHER
MICROBIAL PATHOGENS?

Alan M. Piggot

Fecal indicator bacteria (FIB) are used to assess the quality of
recreational waters because they are correlated with the presence of
several disease-causing organisms. Recently, studies have shown that these
indicator bacteria can reside and grow within foreshore beach sediments at
higher concentrations than the water column. FIB integration into sediment
biofilms may be responsible for the persistence of these bacteria in the
natural environment. Biofilms are matrix-enclosed bacterial communities
attached to surfaces or interfaces. Extracellular polymeric secretions
(EPS) provide the architecture responsible for stabilizing bacterial
communities in high-energy environments, buffering cells from changes in
water chemistry, sequestering nutrients and providing protection against
predation. Interestingly, FIB and other potential pathogens originate from
the human intestine, where attachment to a polysaccharide gel matrix is an
essential step in survival. It is expected that FIB and other pathogens
might use sediment grain biofilms as points of attachment and protective
refugia in the beach sediments. To investigate the relationship between
FIB and biofilms, sediments from the subtidal, intertidal and supratidal
zones were collected from a known nonpoint source polluted beach in Miami,
Florida. EPS was extracted and quantified using a phenol-sulfuric acid
assay. Total microbial and FIB abundances were determined by quantitative
real time PCR (QPCR). Confocal scanning laser microscopy (CLSM) was used
to visualize sediment grain biofilms and attached bacteria to support
quantitative estimates. The purpose of this study is to determine the
potential role of microbial biofilms in the growth, spatial distribution
and mobilization of FIB into the water column at recreational beaches. If
biofilm development is correlated to FIB colonization of beach sediments,
a reevaluation of microbiological quality assessments for recreational
beaches will be needed.

_____________________________________________________________________________

Reef Bioerosion:  What is it and why should we care?
David Weinstein

 

While many aspects of coral reef growth have been highly studied, a disproportionately small amount of research has focused on the mechanisms that reshape, erode and destroy the reef structures.  These mechanisms include bioerosion, physical alterations (storms), and chemical interaction.  Bioerosion, the destruction and removal of calcareous substrate by the direct action of organisms, is critical to the overall functionality of the ecosystem.  Since the Mesoproterozoic era, bioerosional processes have influenced the morphology and sedimentary properties of many carbonate deposits and modern reef systems.  The purpose of this talk is to provide a general understanding of reef bioerosion and the primary eroding organisms.  Significant studies of bioerosional processes will be reviewed in order to highlight the importance of bioerosion in terms of reef modification, reef accretion and paleobathymetry.  Additional bioerosional research and its direct association with reef sedimentology and geomorphology is still necessary in order to provide a more accurate depiction of these geologically and environmentally important structures.

-- 
Monica Arienzo
Division of Marine Geology and Geophysics
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, FL 33149