Ocean Lecture Series

Shifting Baselines: Water Quality in the Central Indian River Lagoon
M. Dennis Hanisak

About the Lecture

The “shifting baselines syndrome” refers to how significant changes to a system are measured against our individual reference points, without consideration of previous experiences.  This syndrome results in a loss of perception of change as each generation redefines what is "natural".

Water quality in the Indian River Lagoon system (IRL) has changed significantly over the past eight decades due to watershed alteration and land drainage patterns. How do those of us living along the lagoon alter its water quality?  How can we establish a baseline for water quality in a lagoon that is so spatially and temporally complex?  How can we avoid the “shifting baselines syndrome”?

Site specific water quality studies, on a frequent sampling interval, are needed to address water quality management issues in the IRL.  Accordingly, high-frequency water quality monitoring, along a perceived water quality and seagrass gradient, has been established at sites in the IRL between northern Vero Beach and Fort Pierce.  Temperature, salinity, dissolved oxygen, pH, turbidity, and chlorophyll a are being continuously monitored with datasonde multiprobes; color, suspended solids, nutrients, and light attenuation coefficients (K) are measured weekly.  Overall, from north to south, salinity increases, while turbidity, color, suspended solids, and chlorophyll a (all attenuators of light) decrease, as do nutrients and K.  Pulses of inorganic nitrogen are associated with the initial onset of the rainy season; secondary peaks, are evident following hurricanes and other major periods of freshwater discharge.  Significant interannual differences in water quality exist that are due to differences in rainfall and related run off.

These findings demonstrate the tremendous human- and climate-related variability in water quality in the IRL.  While the challenges of continued development of our coastal area may appear daunting, these data can also be used in models of expected positive improvements in estuarine health following the reduction of freshwater inputs, which are recognized as the most significant human impacts on the lagoon.

About the Speaker

Dr. Dennis Hanisak is a Research Professor at HBOI/FAU, Director of its Coastal Ecosystems Research Center, and Director of Education.  He has 30 years of experience in marine biology and ecology, with emphasis on marine plants, particularly macroalgae (seaweeds) and seagrasses.  He has worked at Harbor Branch since 1977, conducting research on marine plants in the Indian River Lagoon and in other parts of Florida, the Bahamas, and the Caribbean.

Dr. Hanisak is the author of over 70 scientific publications, a frequently invited participant at national and international meetings and workshops, a past President of the International Phycological Society, and a past President and Chairman of the Board of Trustees of the Phycological Society of America.

As Director of Harbor Branch's Education Program, Dr. Hanisak is dedicated to fostering a deeper understanding and appreciation by students and the public of the importance of the oceans and their impact on our lives.  Among other activities, he leads and develops programs for university students (including the Semester by the Sea program), the Harbor Branch Summer Intern program, innovative programs with St. Lucie County School District (including the establishment of Marine & Oceanographic Academy on the Harbor Branch campus), and the Ocean Science Lecture Series for the public.  It is his belief that working scientists need to convey what they do and why it is important to students, resource managers, and the public, as well as to scientific colleagues.