ON THE DISTRIBUTION AND ECOPHYSIOLOGY OF A RECENLTY
DESCRIBED RAPHIDOPHYTE
Elif Demir1, Kathy J. Coyne2, Ed Whereat2 and David A. Hutchins3
Monterey Bay Aquarium Research Institute, Moss Landing, CA
College of Marine and Earth Studies, University of Delaware, DE
3 Department of Biological Sciences, University of Southern California, CA
1
2
In August 2004, a new raphidophyte species, superficially resembling Heterosigma
akashiwo under light microscopy, formed dense blooms in Delaware’s Inland Bays
(DIB). During environmental sampling in the DIB, it became evident that although it is a
marine species, it has a unique tolerance to low salinity. QPCR analysis of both archived
and recently collected molecular samples demonstrated large variability in its abundance
in three DIB sites over the years 2003-2006. Additionally, broad scale distribution
analysis using PCR, yielded detection in coastal South Carolina and the Delaware Bay
estuary in 2001, although samples from New York, Georgia, Florida were negative.
Fine scale distribution data in DIB obtained in conjunction with environmental
parameters showed a strong positive correlation with lower salinity (< 20) but not with
temperature. These environmental observations were followed up in laboratory culture
experiments focusing on bottom-up control effects on growth. PO43- concentrations
supporting maximum growth rates were 3-20 μM, although active growth was maintained
even at 0.5 μM. PO43- requirements of this new species place it with Chattonella subsalsa
rather than H akashiwo in terms of environmental niche, with a μmax:Ks of 0.85. Culture
experiments also confirmed that this species has a wide salinity (3-18) tolerance towards
the lower end of the spectrum. This is probably is the reason why it can bloom up to
extremely high densities following a rapid salinity change. Top-down control of
microzooplankton grazing was measured in samples collected in June 2005 in Love
Creek in DIB. We determined that microzooplankton do at least occasionally graze on
this species. This study is a first look into the distribution and ecophysiology of this
newly described algae.