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Thorhaug, Anitra [1], Berlyn, Graeme [2], Marcus, Jeffry [3], Schwarz, Arthur [4].

Climate Change Warming in the Marine Benthic Tropics/Subtropical Vegetation: Temperature Data from Waste Heat Predicting Marine Macro-plant Climate Responses.

Tropical/subtropical seagrasses and macro-seaweed for Chlorophyceae and Rhodophyceae from both field and laboratory data live during yearly warm periods near their upper limit temperature limits. We compare this data from waste heat sites with global warming, potentially useful in predicting tropical/subtropical estuarine benthic macrophyte responses to climate change warming. Previously surmised for upper temperature limits of tropical systems, “The tropics are near the brink of disaster” (Thorhaug 1974, Moore, 1958). Many of the marine tropical benthic macrophytes are ancient evolutionarily. These tropical benthic Chlorophyceae and Rhodophyceae evidently did not adapt to temperate or boreal climates over tens of millions of years of marine plant evolution. Seagrasses (unlike macrophytes) secondarily migrated into the marine from terrestrial where temperatures exceed oceanic water temperatures during seasonal warm periods. Thus, theoretically seagrass may be more high-temperature adaptable than tropical macroalgae. Data in field sites including waste heat effluents demonstrate tropical macro-algae upper temperature limits which are lower than seagrasses (except intertidal species) including habitat species such as Laurencia and Halimeda. Among seagrasses there are slightly differing temperature limits among genera with normally deeper growing (Syringodium) more sensitive by a degree C than intertidal genera such as Halodule wrightii or Halophila decipiens. Our 7 year field study showed seagrasses differed with Thalassia, dying approximately 31oC, while Halodule and Halophila found at 2.5oC above control (oscillating diurnal small temperature change). In the central Atlantic Western tropics (Puerto Rico) Thalassia showed 32oC tolerance in waste heat. Global power plant waste heat literature (Thorhaug, 1981) showed similar limits in sites where carefully defined field measurements occurred, dependent on time of exposure. Laboratory data confirmed these time and temperature field data. Summer peak ambient conditions were very close to these upper temperature limits. Field studies over 6 years in heated wastes showed an array of Chlorophyceae and Rhodophyceae dying after steadily exposed to above 30oC over 4d as well as in extensive laboratory data testing seagrasses and macro-algae, confirmed and refined this data. Particularly comprehensive are data from the Chlorophycean single cell organism, Valonia of multiple species, examined for upper temperature limits from all regions of the Caribbean Sea, clearly showing at or above 30.5oC, Valonia was no longer viable. This upper tolerance data was re-measured for membrane bio-electrical, conductance studies, and flux. This showed around 30.0 oC a membrane phase change occurred, hypothesized as related to the higher-order water-structure change (Drost-Hansen and Thorhaug, 1965).

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1 - Greater Caribbean Energy and ENvironment Foundation, 1359 Southwest 22nd Terrace, 1, FL, 33145, usa
2 - Yale University, School Of Foresty & Evironmental Studies, Marsh Hall-360 PROSPECT ST, New Haven, CT, 06511, United States
3 - Miller-Legg , Regional Environmental , 5747 N. Andrews Way, , Ft Lauderdale , FL, 33309, USA
4 - Southwestern Adventist University, Biological Sciences, 214 Woodlawn Dr., Keene, TX, 76059, United States

Marine plants   High Temperature limits
Tropical Seagrass Upper Tempterature Limits
Rhoodopycean High Temperature Limits
Tropical Benthic macrophyte Temperature Limits
Thalassia Temperature Limits
Halodule Upper Temperature Limits..

Presentation Type: Oral Paper
Session: PHYS, Physiology
Location: /
Date: Wednesday, July 21st, 2021
Time: 10:15 AM(EDT)
Number: PHYS002
Abstract ID:198
Candidate for Awards:None

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