Rate of coastal temperature rise adjacent to a warming western boundary current is non-uniform with latitude

Malan, Neil; Roughan, Moninya; Kerry, Colette

doi:10.1002/essoar.10504392.1

Cited by 2 publications

(1 citation statement)

References 46 publications

(58 reference statements)

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“…Our 17‐year‐study period encompassed the loss of kelp as one of the dominant foundation species on these tropicalized reefs (Vergés et al, 2016) and a significant warming trend of 0.23˚C per decade (Malan et al, 2021). We therefore expected to observe declines in temperate fish species, especially those that use kelp as a resource (directly or indirectly) for food, cover and/ or shelter.…”

Section: Discussionmentioning

confidence: 99%

Tropicalization and kelp loss shift trophic composition and lead to more winners than losers in fish communities

Smith

Malcolm

Marzinelli

et al. 2021

Global Change Biology

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Climate‐mediated species redistributions are causing novel interactions and leading to profound regime shifts globally. For species that expand their distribution in response to warming, survival depends not only on their physiological capacity, but also on the ability to coexist or be competitive within the established community. In temperate marine reefs from around the world, the range expansion of tropical species, known as ‘tropicalization’, has been linked to the disappearance of temperate habitat‐forming kelps and shifts to dominance by low‐biomass turfing algae. The consequences of these range expansions and habitat changes on resident fish communities are, however, unclear. Here, we use data derived from baited remote underwater video (BRUV) surveys to analyse changes in diversity and abundance of marine fishes over a 17‐year period in warming reefs that have experienced kelp loss (occurring c. 2009). Despite the loss of kelp, we found that species richness and overall abundance of fishes (measured as probability of occurrence and relative abundance), including both tropical and temperate species, increased through time. We also found dramatic shifts in the trophic composition of fish assemblages. Tropical herbivorous fish increased most markedly through time, and temperate‐associated planktivores were the only group that declined, a potential consequence of tropicalization not previously identified. At the species level, we identified 22 tropical and temperate species from four trophic guilds that significantly increased in occurrence, while only three species (all temperate associated) declined. Morphological trait space models suggest increases in fish diversity and overall occurrence are unlikely to be driven by uniqueness of traits among tropical range expanders. Our results show more winners than losers and suggest that pathways of energy flow will change in tropicalized systems, as planktonic inputs become less important and a higher proportion of algal productivity gets consumed locally by increasingly abundant herbivores.

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Section: Discussionmentioning

confidence: 99%

Tropicalization and kelp loss shift trophic composition and lead to more winners than losers in fish communities

Smith

Malcolm

Marzinelli

et al. 2021

Global Change Biology

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Observed multi-decadal trends in subsurface temperature adjacent to the East Australian Current

Hemming¹,

Roughan²,

Malan³

et al. 2023

Ocean Sci.

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Abstract. Sea surface temperature observations have shown that western boundary currents, such as the East Australian Current (EAC), are warming faster than the global average. However, we know little about coastal temperature trends inshore of these rapidly warming regions, particularly below the surface. In addition to this, warming rates are typically estimated linearly, making it difficult to know how these rates have changed over time. Here we use long-term in situ temperature observations through the water column at five coastal sites between approximately 27.3–42.6∘ S to estimate warming trends between the ocean surface and the bottom. Using an advanced trend detection method, we find accelerating warming trends at multiple depths in the EAC extension region at 34.1 and 42.6∘ S. We see accelerating trends at the surface and bottom at 34.1∘ S but similar trends in the top 20 m at 42.6∘ S. We compare several methods, estimate uncertainty, and place our results in the context of previously reported trends, highlighting that magnitudes are depth-dependent, vary across latitude, and are sensitive to the data time period chosen. The spatial and temporal variability in the long-term temperature trends highlight the important role of regional dynamics against a background of broad-scale ocean warming. Moreover, considering that recent studies of ocean warming typically focus on surface data only, our results show the necessity of subsurface data for the improved understanding of regional climate change impacts.

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Rate of coastal temperature rise adjacent to a warming western boundary current is non-uniform with latitude

Cited by 2 publications

References 46 publications

Tropicalization and kelp loss shift trophic composition and lead to more winners than losers in fish communities

Tropicalization and kelp loss shift trophic composition and lead to more winners than losers in fish communities

Observed multi-decadal trends in subsurface temperature adjacent to the East Australian Current

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