Physiological seasonality in the symbiont and host of the northern star coral, Astrangia poculata
Assessing physiological responses that correspond to the normal range of seasonal variation can provide a better understanding of how environmental stressors may impact physiology. Most tropical corals exhibit seasonal variation in their host and symbiont physiology within a narrow range of environm...
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| Published in: | Coral reefs 2021-08, Vol.40 (4), p.1155-1166 |
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| Main Authors: | , , |
| Format: | Article |
| Language: | eng |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Assessing physiological responses that correspond to the normal range of seasonal variation can provide a better understanding of how environmental stressors may impact physiology. Most tropical corals exhibit seasonal variation in their host and symbiont physiology within a narrow range of environmental conditions. In temperate regions and at the northern end of its distribution,
Astrangia poculata
must adapt to wide ranges in seasonal variability. The species is facultatively symbiotic, and it is unclear if or how symbiotic state and, consequently, host physiology is affected by environmental seasonality. We collected colonies of
A. poculata
with a visible range of symbiotic states from Fort Wetherill State Park in Jamestown, RI in fall, winter, spring, and summer seasons of 2018–2019. We measured physiological parameters, including symbiotic state [chlorophyll (Chl)
a
and
c
2], total lipid content, and stable carbon (
δ
13
C) and nitrogen (
δ
15
N) isotopes of the host and symbiont. Seasonal variation occurred in all physiological parameters we studied. Specifically, Chl
a
,
c
2, and lipid content all reached low points in the spring, suggesting a lag, where the consequences of the coldest temperatures in the winter took up to three months to manifest in the tissue. There were seasonal fluctuations in host:symbiont ratios of
δ
13
C, reflecting changing rates of autotrophy relative to heterotrophy during the year. While some autotrophy occurred during the year, isotopic evidence indicated that carbon acquisition in
A. poculata
was mostly heterotrophic in the winter. Based on
δ
15
N, the symbiont was primarily responsible for nitrogen assimilation, although other sources likely contributed. Both carbon acquisition and nitrogen acquisition were more similar to that of other aposymbiotic coral species, regardless of the symbiotic state of
A. poculata
. Therefore, it may be more appropriate to view
A. poculata
as a unique aposymbiotic coral that is capable of symbiosis, rather than the reverse. |
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| ISSN: | 0722-4028 1432-0975 |