4.2. Environmental drivers of coral condition
Light is typically the primary driver of temporal variations in
maximum photosynthetic yield, although SST has also been suggested
as a key factor. Yields fluctuated most at Pulau Hantu, where
light levels were also the most variable (100e500 PAR). In contrast,
yields were elevated and stable at Labrador where light levels were
consistently low (0e300 PAR). Few papers describe long-term
changes in the photosynthetic capacity of corals in response to
changing environmental conditions and, of those available, findings
vary. Hill and Ralph (2005) did not identify any significant seasonal
variations in the yield, whereas Warner et al. (2002) demonstrated
that fluctuations in coral photosynthetic capacity in the Bahamas
were strongly correlated with seasonal patterns of water temperature
and light, with elevated yields during the cooler months
when surface irradiance levels were high. Higher yields during
cooler months have been noted elsewhere (Piniak and Brown,
2009; Warner et al., 1996), however, these trends are usually
observed in regions characterised by intra-annual changes in
temperatures regime. In the Bahamas, water temperature varied
between 22 C to 34 C, whereas temperatures in Singapore are