Marine algae

The molar and weight ratios of the photosynthetic pigments of ten algal species were
analyzed in an attempt to determine if knowledge of the light field could be used to
give better ratios for estimating the chlorophyll a contributed from each algal division
to total chlorophyll a or biomass. High performance liquid chromatography (HPLC)
is one of the tools used in pigment-based chemotaxonomy for estimating the biomass
of algal communities by determining the concentrations of the various chlorophylls
and carotenoids. Stable ratios of chlorophyll a: marker pigment are used as
multiplying factors for calculating the amount of chlorophyll a contributed from each
major algal group to total chlorophyll a. Stable chlorophyll a : marker pigment ratios
are not always easy to determine, so light field was investigated as a factor for
determining consistently reliable ratios. This data will serve to determine new
chlorophyll a: marker pigment ratios, as well as to verify or suggest changes to the
existing ratios that are currently being used by our research group. An unknown
pigment was isolated from Scytonema sp. grown in higher light fields and the
ecological significance of this pigment was assessed.

The ecosystem created by pelagic Sargassum is important in the life histories of a
number of economically and ecologically important associated organisms. Fishes play a
vital role in this food web and nutrient flow within these systems, but it is unknown how
they locate these floating habitats. This study examined the role of natural chemical cues
from Sargassum patches and the synthetic chemical Dimethylsulfonionpropionate
(DMSP) for an associated fish, the planehead filefish (Stephanolepis hispidus) and a
control fish species not associated with Sargassum, the masked goby (Coryphopterus
personatus). Choice trials with a Y-maze apparatus determined that S. hispidus
responded significantly to chemical cues from Sargassum while C. personatus did not.
DMSP cues did not result in any significant behavioral responses for either fish.
Demonstrating that S. hispidus can respond to chemical cues from Sargassum helps
further our understanding of this unique floating algal reef and how fishes may locate it.

Crustose coralline algae (CCA) are important reef stabilizers and their susceptibility to anthropogenic climate change and ocean acidification (OA) is of concern. Ocean acidification effects on benthic algal communities were determined by the response of CCA, fleshy macroalgae and microalgae to the interaction of pCO2 and light. I examined if elevated pCO2 and light influences CCA dominance by assessing their growth, recruitment and calcification. Elevated pCO2 under natural reef diurnal CO2 cycles did not significantly affect CCA percent cover, calcification rates or survival of adult CCA lobes. No significant community pCO2 effects were observed, rather light controlled dominance. The percent cover of microalgae increased in highlight, while CCA increased in the shade. My results indicate that algal response to irradiance is a more significant driver of reef benthic algal change than pCO2 levels predicted for 2100; however, this conclusion should be corroborated in longer-term and in field experiments.