Ecological Assessment of Algae
So much more than pond scum
Despite the unflattering images of "pond scum" that many people often associate with algae, marine macrophytes have proven to be among the most diverse, ecologically important, common and beautiful organisms present in tropical reef systems.
Phycologists at the Coral Reef Ecosystem Division (CRED) use algal communities to address the following questions:
- What is the best way to quantify algal functional groups (e.g., macroalgae, crustose coralline algae [CCA], and turf algae) in tropical reef settings?
- What species are present in each island ecosystem and in what quantity?
- Do changes in algal populations serve as a good environmental indicator of reef health?
- How do algal diversity and abundance change over time?
- Can biogeographical hypotheses be formulated about algal dispersal and evolution using qualitative and quantitative data from island groups around the Pacific?
Characterizing the algal communities in a reef system
Algal populations are assessed using a line-point-intercept method (LPI). CRED started using this method in 2008 (in conjunction with surveys of percent cover of corals and macroinvertebrates). Previously, CRED relied on a photoquadrat method as its primary field method for species-level estimates of algal cover.
What are we learning from algal communities?
The importance of algae to the ecosystem is staggering:
- Algae form the base of the food web
- Some species occupy much of the available substrate
- They help oxygenate the ocean for animal life to thrive
- Healthy coral tissue often requires microscopic symbiotic algae for survival: if algae are expelled from coral tissue because of stress, coral bleaching occurs—a scenario that is becoming all too real in many geographic locations
Although large, fleshy algal forms are the most recognizable floral components on reefs to most divers, tiny turf algae and CCA also are widespread and play significant roles in ecosystems. Turf algae are the first to colonize vacant substrate and cover essentially every nonliving hard surface on a reef. Turf algae also are among the most important food sources for herbivorous fishes and invertebrates. Relatively fast-growing CCA act as glue on reefs, cementing loose components of a reef system together, and serve as a settling surface for larval invertebrates and other algae. Without CCA holding everything together, much of a reef would be washed into deep water or onto shore during heavy storms.
Without algae, there would be no tropical reef ecosystems
Marine algae are among the least studied and least understood reef organisms. Research is needed sorely to catalog and quantify the species that are present on reef systems around the Pacific, and ecological studies are necessary to examine the role of these critical plants in reef ecosystems.
Floras of algal communities around remote U.S. Pacific islands are being described by CRED staff in conjunction with researchers from the Bishop Museum in Honolulu. So far, algal communities from the following locations have been described:
- French Frigate Shoals, Northwestern Hawaiian Islands (Vroom et al. 2006a)
- Howland and Baker Islands, U.S. Phoenix Islands (Tsuda et al. 2008)
- Gardner Pinnacles, Northwestern Hawaiian Islands (Vroom and Timmers 2009)
- Johnston Atoll (Tsuda et al. 2010a)
- Wake Atoll (Tsuda et al. 2010b)
- Swains Island, American Samoa (Tsuda et al. 2011)
- Kingman Reef and Jarvis Island, U.S. Line Islands (Tsuda et al. 2012a)
- Santa Rosa Reef, Mariana Archipelago (Tsuda et al. 2012b)
- Rose Atoll, American Samoa
- Manua Islands, American Samoa
- Northern Mariana Islands
Analyses of voucher specimens collected during CRED's Pacific Reef Assessment and Monitoring Program expeditions has led to the discovery and description of new species to science and of a previously unknown reproductive processes in one of the most ubiquitous algae in the Northwestern Hawaiian Islands, the green alga Halimeda velasquezii:
- Acrosymphyton brainardii (Vroom and Abbott 2004a)
- Scinaia huismanii (Vroom and Abbott 2004b)
- Dasya atropurpurea (Vroom 2005)
- Halimeda kanaloana (Verbruggen et al. 2006)
- Halimeda velasquezii reproduction (Vroom and Smith 2003)
In addition to the discovery of new species, our field sampling methods, photoquadrat and LPI, were used to successfully complete detailed analyses of benthic cover on reefs surrounding the following areas:
- French Frigate Shoals, Northwestern Hawaiian Islands (Vroom et al. 2005)
- Pearl and Hermes Atoll, Northwestern Hawaiian Islands (Page 2006, Page-Albins et al. 2012)
- Gardner Pinnacles, Northwestern Hawaiian Islands (Vroom and Timmers 2009)
- Howland and Baker Islands, U.S. Phoenix Islands (Vroom et al. 2010)
- Palmyra Atoll, U.S. Line Islands (Braun et al. 2009)
- Northwestern Hawaiian Islands (the entire island chain; Vroom and Braun 2010)
- Necker Island, Northwestern Hawaiian Islands (Schopmeyer et al. 2011)
- Anatahan, Commonwealth of the Northern Mariana Islands (Vroom and Zgliczynski 2011)
- Mariana Archipelago (the entire island chain)
Results from CRED algal surveys at the above-mentioned healthy, fairly unimpacted islands reveal that most reef habitats there contain abundances of algal functional groups, including macroalgae, in conjunction with corals. Some areas where we work even appear to be naturally dominated by algae rather than scleractinian coral species (Friedlander et al. 2004), in response to local physical and environmental conditions. The Northwestern Hawaiian Islands, for instance, contain vast macroalgal meadows that form essential habitat for juvenile fishes and invertebrates (Vroom and Braun 2010). However, this finding doesn't negate the detrimental effects of algal blooms and phase shifts that have occurred in ecosystems affected by human activities, or that can naturally occur in remote reefs (such as the Boodlea bloom documented at Kure and Midway Atolls in 2008; Vroom et al. 2009). Additionally, algal composition on U.S. Pacific reefs may be altered by events like the 2002 and 2004 coral bleaching episodes observed at Kure and Midway Atolls (Vroom and Page 2006), hurricane activity (Tribollet and Vroom 2007; Tribollet et al. 2010), or volcanic eruptions (Vroom and Zgliczynski 2011). As long as reef systems can regain their natural balance within a few years after such catastrophes, they are likely to remain healthy and resilient.
Full references for the papers cited on this page.
2009. Examination of algal diversity and benthic community structure at Palmyra Atoll, U.S. Line Islands. Proceedings of the 11th International Coral Reef Symposium, 7-11 July 2008, Ft. Lauderdale, Florida, Session Number 18: 865-869.
2004. Status of coral reefs in the Hawaiian Archipelago. In: Wilkinson C (ed.) status of coral reefs of the world: 2004, vol. 2: 411-430. Australian Institute of Marine Science, Townsville, Queensland, Australia. OLD
2006. Factors influencing benthic distributional patterns in a near-pristine coral reef ecosystem: Pearl and Hermes Atoll. Master's thesis, University of Hawaiʻi at Mānoa, 127 p.
2012. Patterns in benthic communities at a remote subtropical atoll along a wave exposure gradient. Pacific Science. Early view available online at http://pacificscience.files.wordpress.com/2012/03/pac-sci-early-view-66-4-6.pdf.
2004. A Rapid Ecological Assessment (REA) quantitative survey method for benthic algae using photo quadrats with scuba. Pacific Science 58: 201-209.
2011. Spatial and temporal comparisons of benthic communities at Necker Island, Northwestern Hawaiian Islands. Pacific Science 65: 405-417.
2010. Spatial-temporal variability in macroalgal assemblages of American Samoa. Phycologia 49: 574-591.
2007. Temporal and spatial comparison of the relative abundance of macroalgae across the Mariana Archipelago between 2003 and 2005. Phycologia. 46: 187-197.
2010a. Marine benthic algae from Johnston Atoll: new species records, spatial distribution, and taxonomic affinities with neighboring islands. Pacific Science 64: 581-601.
2011. First records of marine benthic algae from Swains Island, American Samoa. Cryptogamie Algologie 32: 271-291.
2012a. Floristic account of the marine benthic algae from Jarvis Island and Kingman Reef, Line Islands, Central Pacific. Micronesica 43: 14-50.
2010b. New records of subtidal benthic marine algae from Wake Atoll, Central Pacific. Botanica Marina 53: 19-29.
2008. Additional marine benthic algae from Howland and Baker Islands, Central Pacific. Pacific Science 62: 271-290.
2012b. New marine algal records from the Polynesia-Micronesia region of the Pacific Ocean. Marine Biodiversity Records. DOI: 10.1017/S1755267212000024
2006. Phylogeny and taxonomy of Halimeda incrassata, including descriptions of H. kanaloana and H. heteromorpha spp. nov. (Bryopsidales, Chlorophyta). European Journal of Phycology 41: 337-362.
2005. Dasya atropurpurea sp. nov. (Ceramiales, Rhodophyta), a deep-water species from the Hawaiian Archipelago. Phycologia 44: 572-580.
2011. "Coral Dominance": a dangerous ecosystem misnomer? Journal of Marine Biology 2011, Article ID 164127, 8 p. DOI: 10.1155/2011/164127
2004a. Acrosymphyton brainardii sp. nov. (Gigartinales, Rhodophyta) from French Frigate Shoals, Northwestern Hawaiian Islands. Phycologia 43: 68-74.
2004b. Scinaia huismanii sp. nov. (Nemaliales, Rhodophyta): an addition to the exploration of the marine algae of the Northwestern Hawaiian Islands. Phycologia 43: 445-454.
2009. Macroalgal (Boodlea composita) bloom at Kure and Midway Atolls, Northwestern Hawaiian Islands. Botanica Marina 52: 361-363.
2010. What is the benthic composition of a healthy subtropical reef? Baseline species-level percent cover, with an emphasis on reef algae, in the Northwestern Hawaiian Islands. PLoS ONE 5: e9733. DOI: 10.1371/journal.pone.0009733
2010. Marine biological community baselines in unimpacted tropical ecosystems: spatial and temporal analyses of reefs at Howland and Baker Islands. Biodiversity and Conservation 19: 797-812. DOI: 10.1007/s10531-009-9735-y
2006. Relative abundance of macroalgae (RAM) on Northwestern Hawaiian Island reefs. Atoll Research Bulletin 543: 533-548.
2006b. Algae-dominated reefs. American Scientist 94: 429-437.
2005. Spatial heterogeneity of benthic community assemblages with an emphasis on reef algae at French Frigate Shoals, Northwestern Hawaiian Islands. Coral Reefs 24: 574-581.
2006a. Marine algae of French Frigate Shoals, Northwestern Hawaiian Islands: species list and biogeographic comparisons. Pacific Science 60: 81-95.
2003. Reproductive features of Hawaiian Halimeda velasquezii (Bryopsidales, Chlorophyta), and an evolutionary assessment of reproductive characters in Halimeda. Cryptogamie, Algologie 24: 355-370.
2009. Spatial and temporal comparison of algal biodiversity and benthic cover at Gardner Pinnacles, Northwestern Hawaiʻian Islands. Journal of Phycology 45: 337-347.
2011. Effects of volcanic ash deposits on four functional groups of a coral reef. Coral Reefs 30: 1025-1032.