Factors Limiting the Range Extension of Corals into High-Latitude Reef Regions

Abstract

Reef-building corals show a marked decrease in total species richness from the tropics to high latitude regions. Several hypotheses have been proposed to account for this pattern in the context of abiotic and biotic factors, including temperature thresholds, light limitation, aragonite saturation, nutrient or sediment loads, larval dispersal constraints, competition with macro-algae or other invertebrates, and availability of suitable settlement cues or micro-algal symbionts. Surprisingly, there is a paucity of data supporting several of these hypotheses. Given the immense pressures faced by corals in the Anthropocene, it is critical to understand the factors limiting their distribution in order to predict potential range expansions and the role that high latitude reefs can play as refuges from climate change. This review examines these factors and outlines critical research areas to address knowledge gaps in our understanding of light/temperature interactions, coral-Symbiodiniaceae associations, settlement cues, and competition in high latitude reefs.

Regional and global climate risks for reef corals: Incorporating species‐specific vulnerability and exposure to climate hazards

“…Poleward range expansions of corals are also observed in many regions today (Baird et al, 2012; Denis et al, 2013; Marsh, 1993; Precht & Aronson, 2004; Yamano et al, 2011). Our results suggest that high‐latitude regions are likely to pose less climate risk to tropical corals (Figure 3; Figure S3), especially if corals are capable of migrating beyond their current geographic ranges (but see Abrego et al, 2021 for drivers limiting latitudinal distribution of reef corals including various physical and biotic factors). On the contrary, current high‐latitude residents are projected to suffer substantial regional climate risks akin to tropical corals in the tropics (Figure 4).…”

Are corals coming to a reef near you? Projected extension of suitable thermal conditions for hard coral communities along the east Australian coast

“…Other factors that might limit coral establishment and/or persistence at higher latitudes include light availability, nutrient levels, sediment loads, ocean acidification, larval dispersal, competition for space with other resident habitat‐forming species (e.g. kelp), and availability of suitable settlement sites and cues (Abrego et al, 2021). The combined effects of these abiotic and biotic factors will vary amongst species and latitudes (Abrego et al, 2021; Madin et al, 2016).…”

“…Successful range extensions at the poleward range edge for marine species are dependent on conditions at a new location being suitable for larval settlement and long‐term survival (persistence) and there being a supply of competent larvae (Abrego et al, 2021). In eastern Australia, larval supply is facilitated by the East Australian Current (EAC), which flows southward at speeds of up to 4.68 km h −1 (Roughan & Middleton, 2004).…”

High-latitude marginal reefs support fewer but bigger corals than their tropical counterparts

“…Reefs with higher rugosity and thus complexity have been shown to support more smaller corals (Crabbe, 2010). Competition can also affect coral sizes, such as competition for space with other non-coral, sessile benthic organisms like algae, corallimorpharians and zoanthids (Abrego et al ., 2021; Reimer et al ., 2021). These biotic interactions may reduce the rate at which corals grow (Chadwick & Morrow, 2011), so that reefs with a higher cover of other benthic taxa could have fewer or smaller corals than expected.…”

“…The copyright holder for this preprint this version posted October 21, 2022. ; https://doi.org/10.1101/2022.10.20.513025 doi: bioRxiv preprint classically favoured by coral reef ecologists, and 2) a novel compositional functional regression approach (Talská et al, 2018) that has not been used in this context despite its potential. At higher latitudes, where conditions are harsh due to extremes in temperature, light levels and storm events, we expect fewer small coral colonies, because coral mortality rates are generally highest for the smallest corals (Connell, 1973), and sexual recruitment rates are low (Harriott & Banks, 1995;Abrego et al, 2021;Cant et al, 2022). Potential differences in population size structure of corals along this environmental gradient might indicate the effect of stress on coral population dynamics, providing a lens to the future, where reefs might be affected by increased disturbances as a result of climate change.…”