Abstract Detail

From High Islands to the Ocean Floor: Pacific Island Plants at the Extreme

Gibson, Veronica [1], Smith, Celia [1].

Integrated physiological response by four red algae species and analysis of benthic community structure across an environmental gradient of tidally-driven submarine groundwater discharge conditions.

While polluted submarine groundwater discharge (SGD) has been linked to algal bloom conditions on nearshore reefs, neither macroalgal physiological response to SGD nor benthic community structure under SGD conditions are well understood. A cryptic yet common feature on basaltic coastlines, SGD in Hawaiʻi delivers tidally-driven diurnal and semidiurnal pulses of fresh, nutrient rich basal groundwater to nearshore ecosystems. SGD influenced nearshore ecosystems are characterized by extreme daily changes in salinity, pH, temperature, and nutrient availability, which oscillate between ambient and oligotrophic open ocean conditions during high tides and SGD conditions of fresher, cooler, and more nutrient rich waters during low tides. In this study, field characterization across a gradient of polluted SGD influence measures physiological responses in photosynthesis and tissue water potential regulation by four macroalgal species to SGD conditions at Wailupe Beach. Additionally, benthic analyses describe community diversity and structure across an SGD gradient for three sites. SGD flux quality and volume is further influenced by wind, wave action, hydrologic changes, and anthropogenic nutrient pollution. Natural gradients of SGD influence on nearshore reefs may have provided strong selective pressures on macroalgal species. To examine the influence of SGD on nearshore macroalgal physiology and ecology a multi-factor analysis was undertaken. Comparisons are made across two species pairs, closely related invasive Gracilaria salicornia and cryptogenic Hydropuntia perplexa, and invasive Acanthophora spicifera and closely related native Laurencia dendroidea. Measurably different physiological responses are exhibited across this environmental gradient. Benthic analyses reveal the highest macroalgal coverage and lowest diversity nearest to SGD seeps, while higher diversity and lower macroalgal coverage occurred at offshore, non-SGD influenced sites. We discuss implications for the role of SGD and groundwater pollution on community reef dynamics, competition, and phase shifts from coral to algae dominated systems.

Related Links:
Veronica Gibson Research Site

1 - University of Hawaiʻi at Mānoa, School of Life Sciences, 3190 Maile Way, Honolulu, HI, 96822, US

osmotic relations
environmental gradient
nutrient pollution

Presentation Type: Symposium Presentation
Number: S6003
Abstract ID:1043
Candidate for Awards:Ecological Section Best Graduate Student Paper,Physiological Section Physiological Section Li-COR Prize,Physiological Section Best Paper Presentation

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