Effects of elevated water temperature and food availability on the reproductive performance of a coral reef fish

Abstract

Climate change is predicted to increase ocean temperatures and alter plankton communities that are food for many marine fishes. To examine the effects of increased sea surface temperature and fluctuating food levels on reef-fish reproduction, breeding pairs of the coral reef damselfish Acanthochromis polyacanthus were maintained for a full summer breeding season in an orthogonal experiment comprising 3 temperature and 2 food levels. Water temperatures were the current-day average summer temperature for the collection location (28.5°C) and temperatures predicted to become close to the average for this region over the next 50 to 100 yr (30.0 and 31.5°C). Pairs were fed either a high or low quantity diet based on average and minimum feeding rates in the wild. Both water temperature and food supply affected reproductive output. Fewer pairs bred at elevated water temperatures and no pairs reproduced at either of the higher temperatures on the lower quantity diet. Furthermore, eggs produced were smaller at 30.0 and 31.5°C compared to those at 28.5°C. Histological analysis of the gonads and steroid hormone measurement did not reveal any apparent differences in patterns of oogenesis among treatments. However, spermatogenesis was reduced at high temperatures despite some increases in plasma androgen levels. Reduced breeding rate at warmer temperatures combined with reduced sperm production indicates the potential for significant declines in A. polyacanthus populations as the ocean warms.

Effects of climate change on fish reproduction and early life history stages

“…This supports the view that all species are likely to show similar responses to rising temperatures, but that the thresholds for these effects will vary in relation to specific thermal tolerance ranges. There is also some evidence that the ranges over which normal function can be maintained may be broader in cool-water and temperate species than among tropical species (Nilsson et al 2009;Donelson et al 2010).…”

“…For example, spiny damselfish, Acanthochromis polyacanthus, spawn in spring and early summer on Australia's Great Barrier Reef, and show temperature inhibition of ovarian steroidogenesis above 308C (Donelson et al 2010; N. W. Pankhurst, P. M. Pankhurst and L. Gonzalez-Reynoso, unpubl. data).…”

“…Single-domain temperature experiments also generally ignore the synergistic interaction of temperature with other physical and biotic variables. Temperature effects on reproduction can be differentially expressed under different photoperiod regimes (Pankhurst and Porter 2003) and recent experiments on tropical damselfish show that temperature effects are modulated by nutritional status (Donelson et al 2010). Finally, some species exhibit variation in thermal reaction norms across their geographic range that indicates some capacity for acclimation and adaptation to temperature gradients (Angilletta 2009;Gardiner et al 2010), and potentially to a changing climate.…”

Neustonic copepods (Labidocera spp.) discovered living residentially in coral reefs

“…Copepods that live residential to specific benthic environments emerge only temporarily into the water column, typically during the night (Ohlhorst 1982;Mauchline 1988), taking advantage of the sheltering darkness to forage for food while avoiding visual predators (Zaret and Suffern 1976;Alldredge and King 1985). During the day these copepods may live amongst or above the substrate (Alldredge and King 1977), swarm in the hyperbenthic layer above the seafloor (Carleton and Hamner 2007; Relatively little is known about the behavior and life histories of copepods living in coral reefs, even though they are pertinent for coral health, fisheries production, and nutrient cycling within reefs (Ikeda et al 1982;Hamner et al 1988;Carleton 1993;Donelson et al 2010;Ferrier-Pagès et al 2011). Some holoplanktonic groups (i.e.…”

Dynamic resource allocation between pre- and postcopulatory episodes of sexual selection determines competitive fertilization success

“…For example, a low-quantity diet is known to negatively affect reproductive output (e.g. [16]), whereas high food quality positively influences male reproductive performance (e.g. [17]), for instance by enhancing sperm competitiveness [18].…”