Crustose Coralline Algae Ecology and Systematics
I’m interested in the ecology, evolution and conservation biology of crustose coralline algae (CCA). CCA are red algae that calcify and encrust on the benthos in tropical and temperate marine habitats. Importantly, these algae play a critical role in many habitats as preferred substrata for invertebrate settlement. While these algae can be very common on hard substrates they are surprisingly poorly studied. One problem is that identifying the species requires microscopic or genetic work that is difficult in the field. With an extensive skill set I study multiple aspects of CCA diversity, ecology and response to climate change.
I’ve been studying the ecological role of CCA and how different species of CCA can impact recruitment (Ritson-Williams et al., 2009). I’ve been using coral larvae to test multiple hypotheses about coral recruitment: Are CCA required for coral larval settlement? No, in many of my experiments coral larvae will settle in response to a biofilm without any CCA present (Ritson-Williams et al., 2010). Do all species of CCA induce the same rates of settlement? No, in fact it appears that only a few species of CCA facilitate coral settlement including Hydrolithon boergesenii and Titanoderma prototypum (Ritson-Williams et al., 2014). Do all species of coral have larvae that prefer to settle on CCA compared to a natural biofilm? Sort of, it seems that all species of coral larvae have high rates in response to the facilitating species, but for the corals that brood their larvae we see that they also have high rates of settlement in response to biofilms (Ritson-Williams et al., 2016). Can we use CCA to increase coral recruitment in a restoration setting? Maybe, I am actively working with SECORE to test how we might use facilitating species to help restore reefs, and additionally I am training restoration practitioners in CCA ecology and identification to help improve our capacity for restoration. I am also very interested in the potential role of CCA in the recruitment of other invertebrates such as abalone, an important fishery in California.
Our poor understanding of the species diversity of coralline algae is hampering our ability to understand how these species interact, drive ecosystem processes and are stressed by local and global threats. I am very interested in researching the impact of global chang on CCA diversity and ecology. Even though we know that temperature stress and ocean acidification can greatly hamper CCA recruitment and calcification, we don’t have a good understanding of how these stressors are changing communities in the field. Are some species being lost from the wild? Is there a change in competitive interactions? Can CCA acclimate and adapt to climate change? These are critical questions if we are going to ensure the persistence of CCA in future ecosystems.
To better understand CCA diversity I study their genetics and systematics. Classic phylogenies relied on morphological features to group species into genera and families, but molecular genetics is providing more information on their evolutionary relationships. I’ve been using the psbA (a gene found in the chloroplast), COI (mitochondria) and SSU (ribosomal) gene regions to construct a phylogeny of Caribbean CCA. This phylogeny is providing novel information on evolutionary relationships and has identified gene regions that can be used to barcode species. This barcode will be invaluable for researchers to identify species of CCA without being trained in CCA morphology and taxonomy.
Corresponding with this genetic collection I’ve been taking SEM images of the microscopic features that taxonomists use to identify each species. These detailed microscopic images are paired with my in situ live photographs of each species. These images are a valuable resource as currently there are no field guides for Caribbean CCA species. I’m using morphological data and these images to build a species page for each species of CCA in the Caribbean. As part of my commitment to open data I have provided these species pages as PDF’s on this website (see below to download). I hope that these guides will help everyone to better understand the distribution, abundance and ecology of different species of CCA so that we an better document changes that are occurring on reefs.
I’ve been studying the ecological role of CCA and how different species of CCA can impact recruitment (Ritson-Williams et al., 2009). I’ve been using coral larvae to test multiple hypotheses about coral recruitment: Are CCA required for coral larval settlement? No, in many of my experiments coral larvae will settle in response to a biofilm without any CCA present (Ritson-Williams et al., 2010). Do all species of CCA induce the same rates of settlement? No, in fact it appears that only a few species of CCA facilitate coral settlement including Hydrolithon boergesenii and Titanoderma prototypum (Ritson-Williams et al., 2014). Do all species of coral have larvae that prefer to settle on CCA compared to a natural biofilm? Sort of, it seems that all species of coral larvae have high rates in response to the facilitating species, but for the corals that brood their larvae we see that they also have high rates of settlement in response to biofilms (Ritson-Williams et al., 2016). Can we use CCA to increase coral recruitment in a restoration setting? Maybe, I am actively working with SECORE to test how we might use facilitating species to help restore reefs, and additionally I am training restoration practitioners in CCA ecology and identification to help improve our capacity for restoration. I am also very interested in the potential role of CCA in the recruitment of other invertebrates such as abalone, an important fishery in California.
Our poor understanding of the species diversity of coralline algae is hampering our ability to understand how these species interact, drive ecosystem processes and are stressed by local and global threats. I am very interested in researching the impact of global chang on CCA diversity and ecology. Even though we know that temperature stress and ocean acidification can greatly hamper CCA recruitment and calcification, we don’t have a good understanding of how these stressors are changing communities in the field. Are some species being lost from the wild? Is there a change in competitive interactions? Can CCA acclimate and adapt to climate change? These are critical questions if we are going to ensure the persistence of CCA in future ecosystems.
To better understand CCA diversity I study their genetics and systematics. Classic phylogenies relied on morphological features to group species into genera and families, but molecular genetics is providing more information on their evolutionary relationships. I’ve been using the psbA (a gene found in the chloroplast), COI (mitochondria) and SSU (ribosomal) gene regions to construct a phylogeny of Caribbean CCA. This phylogeny is providing novel information on evolutionary relationships and has identified gene regions that can be used to barcode species. This barcode will be invaluable for researchers to identify species of CCA without being trained in CCA morphology and taxonomy.
Corresponding with this genetic collection I’ve been taking SEM images of the microscopic features that taxonomists use to identify each species. These detailed microscopic images are paired with my in situ live photographs of each species. These images are a valuable resource as currently there are no field guides for Caribbean CCA species. I’m using morphological data and these images to build a species page for each species of CCA in the Caribbean. As part of my commitment to open data I have provided these species pages as PDF’s on this website (see below to download). I hope that these guides will help everyone to better understand the distribution, abundance and ecology of different species of CCA so that we an better document changes that are occurring on reefs.
Caribbean Crustose Coralline Algae Species Pages
Titanoderma prototypum
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This species is very rare on most Caribbean reefs, but an important facilitator of coral larval settlement.
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Titanoderma bermudense
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This species is very rare and looks very similar to T. prototypum. It has never been tested for its influence on coral larval settlement.
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Hydrolithon boergesenii
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This species can be common in certain habitats and is an important facilitator of coral larval settlement.
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Paragoniolithon solubile
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This species is very common and can dominate some reefs. It can also be found overgrowing corals. This species does not facilitate coral larval settlement.
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Porolithon pachydermum
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This species is very common in shallow high light environments, especially on the tops of spurs. This species inhibits coral larval settlement.
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