Presentation Title

Effects of low tide exposure on photosynthetic potential of the intertidal seaweed Silvetia compressa

Faculty Mentor

William J. Hoese, Jennifer L. Burnaford

Start Date

18-11-2017 9:59 AM

End Date

18-11-2017 11:00 AM

Location

BSC-Ursa Minor 66

Session

Poster 1

Type of Presentation

Poster

Subject Area

biological_agricultural_sciences

Abstract

Organisms in the rocky intertidal zone are exposed to marine and terrestrial stressors daily. Conditions during low-tide emersion can be particularly stressful for sessile organisms such as the seaweed Silvetia compressa. We hypothesized that exposure to high light or high temperature during emersion would decrease photosynthetic potential and inhibit recovery of S. compressa, and that these factors would have strong effects when combined, especially with repeated emersion. We conducted a two-day manipulative experiment with one ‘no low tide’ and four ‘experimental low tide’ treatments with combinations of two levels of temperature and light (high/low), maintaining fronds in high-tide conditions between exposures (n=10 S. compressa individuals). We measured maximum quantum yield (MQY) as an indicator of photosynthetic potential before and after each low tide and again following the final recovery period. Fronds exposed to high light showed greater declines in MQY during emersion than fronds exposed to low light. After one high tide recovery period, at the start of the second low tide, MQY in the ‘high light, high temperature low tide’ treatment was, on average, 77% of original levels, while MQY in all other treatments exceeded 85% of original levels. This negative effect was magnified after two successive low tides, suggesting that high temperature exacerbates the strong negative effects of high light levels on S. compressa, potentially by inhibiting repair pathways. Understanding the impact of low-tide exposure on ecologically significant species such as S. compressa is essential to enable us to predict the effect of climate change on intertidal systems.

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Nov 18th, 9:59 AM Nov 18th, 11:00 AM

Effects of low tide exposure on photosynthetic potential of the intertidal seaweed Silvetia compressa

BSC-Ursa Minor 66

Organisms in the rocky intertidal zone are exposed to marine and terrestrial stressors daily. Conditions during low-tide emersion can be particularly stressful for sessile organisms such as the seaweed Silvetia compressa. We hypothesized that exposure to high light or high temperature during emersion would decrease photosynthetic potential and inhibit recovery of S. compressa, and that these factors would have strong effects when combined, especially with repeated emersion. We conducted a two-day manipulative experiment with one ‘no low tide’ and four ‘experimental low tide’ treatments with combinations of two levels of temperature and light (high/low), maintaining fronds in high-tide conditions between exposures (n=10 S. compressa individuals). We measured maximum quantum yield (MQY) as an indicator of photosynthetic potential before and after each low tide and again following the final recovery period. Fronds exposed to high light showed greater declines in MQY during emersion than fronds exposed to low light. After one high tide recovery period, at the start of the second low tide, MQY in the ‘high light, high temperature low tide’ treatment was, on average, 77% of original levels, while MQY in all other treatments exceeded 85% of original levels. This negative effect was magnified after two successive low tides, suggesting that high temperature exacerbates the strong negative effects of high light levels on S. compressa, potentially by inhibiting repair pathways. Understanding the impact of low-tide exposure on ecologically significant species such as S. compressa is essential to enable us to predict the effect of climate change on intertidal systems.