Author name(s): Liana Lerma*, David Hicks
*primary corresponding author: Liana Lerma, Biological Sciences Department,
University of Texas Brownsville, 80 Fort Brown, Brownsville, Texas, 78575;
l.lerma7@gmail.com; 956-882-5883
Biography: Liana Lerma is a graduate from the University of Texas at Brownsville
where she received a Master of Science in Biology. She also received a Bachelor of
Science in Biomedical Science from Texas A&M University. She has had the privilege of
being supported by Texas Sea Grant to do research on South Padre Island and wishes to
pursue a Ph.D in the field of marine science in the near future.
Presentation type: Oral (PowerPoint)
Presentation title: The effects of a red tide, Karenia brevis episode on the benthic
macroinvertebrate communities of South Padre Island, Texas
Abstract: South Padre Island, Texas has experienced increasing frequency of red tide
blooms (Karenia brevis) since the 1900s, many of which resulted in massive fish kills. In
addition, shorebirds and other terrestrial wildlife deaths have been linked to K. brevis
blooms prompting investigations of potential pathways by which brevetoxins may be
transmitted to higher trophic levels. The benthic macrofanual community inhabiting the
swash zone of sandy beaches consists of filter feeding invertebrates which may serve as
toxin bioaccumulators to secondary consumers of both marine and terrestrial food webs.
In September 2011, South Padre Island was impacted by a four month long red tide
event, killing a total of 4.4 million fish. The effects of K. brevis on benthic communities
are largely undocumented and the few studies that have been conducted often produce
conflicting results. Therefore, the purpose of this study was to assess the effects of K.
brevis on the benthic macroinvertebrate community following the 2011 harmful algal
bloom. Sampling was conducted from six 400m stretches of beach prior to and after a
prolonged period of high red tide cell count concentrations. Species identification,
abundances, and biomass were obtained from each sample. A one-way ANOSIM
indicated that the pre and post bloom abundances and biomass were significantly
different (ANOSIM Global R=0.612, P=0.01 and R=0.538, P= 0.01, respectively). Pre
and post bloom species abundances and biomass were 68.5% and 67.0% similar
respectively. Pre and post community differences were contributed to greater abundances
and biomass of S. squamata in the pre-bloom samples and greater abundances of D.
variabilis and A. depressus in the post-bloom samples. Multi-dimensional scaling
analyses also indicated a distinct separation of the before and after red tide communities
in both abundances and biomass. However, when compared with other long term data
sets the variation among pre and post bloom communities is similar suggesting that
seasonal variation rather than the effects of K. brevis may account for the differences
between pre and post bloom communities.