On a narrow stretch along the northern-central coast of Chile, the seagrass Heterozostera nigricaulis (syn. Zostera nigricaulis, Heterozostera tasmanica) occurs in three isolated patches no more than 300 km apart. It is a common intertidal to subtidal seagrass in the Zosteracea family and is found growing in protected and soft-bottom areas. Heterozostera nigricaulis is native to the southern coast of Australia (Coyer et al. 2013), from where it colonized Chile some 100s to 1000s years ago (Smith et al. 2018). In Australia, they form extensive meadows that produce large quantities of non-buoyant seeds and specialized vegetative rhizomes used for dispersal (Thomson et al. 2015, Smith et al. 2016, 2018). In Chile, however, H. nigricaulis was never found to flower or produce seeds. Instead, they likely grow only vegetatively, as suggested by a recent study that found the three populations to consist of only two non-flowering clones that are not mixed (Smith et al. 2018).
The seagrass meadow of H. nigricaulis at Puerto Aldea is situated in the southern part of the Tongoy Bay, at a small fishing caleta. It has a continuous distribution at 1 to 6 m depth (personal observation) and is protected from onshore winds and waves by the headland Punta Lengua de Vaca, which is an important upwelling zone. The spatial extent of the meadow is about 1.2 km2 (Phillips et al. 1983) where it also grows under the jetty of the fishing caleta. Due to its remoteness and rare occurrence, H. nigricaulis is classified as endangered by the Chilean Ministry of Environment (https://clasificacionespecies.mma.gob.cl/).
To date 117 different species of macroinvertebrates and 16 fish species have been reported from the seagrass meadow at Puerto Aldea (González 1990), but most likely the diversity is even higher. The meadow at Puerto Aldea is habitat to the commercially exploited species such as Argopecten purpuratus (scallop) and Romaleon setosum (crab) (Pérez-Matus et al. 2005, SUBPESCA Chile). Consequently, artisanal fishers use the meadow to extract scallops and they have recognized that it serves as an ideal nursery ground for this species, i.e. without seagrass there are no natural scallop populations. For this reason, the fishers protect their seagrass meadow (personal communication). It is estimated that about 30 artisanal fishers are associated to the fishing caleta (SUBPESCA Chile) at Puerto Aldea. As H. nigricaulis seagrass meadows are rare in Chile but provide important ecosystem services, e.g., livelihoods for fishers and efficient carbon sinks (nature-based climate change solutions), their protection must become an important priority in Chile.
Coyer JA, Hoarau G, Kuo J, et al. 2013. Phylogeny and temporal divergence of the seagrass family Zosteraceae using one nuclear and three chloroplast loci. Systematics and Biodiversity 11:271–284.
González SA 1990. Heterozostera tasmanica (Martens ex Aschers.) den Hartog y comunidad asociada en el norte de Chile. Pre-graduate thesis in Spanish. Universidad Católica del Norte, Chile.
Pérez-Matus A, Cifuentes M, Araya P et al. 2005. Solitary seagrass meadow in Chile supports a unique scallop garden.JMBA Global Marine Environment 2:1-4.
Phillips RC, Santelices B, Bravo R, McRoy CP 1983. Heterozostera tasmanica (Martensex Aschers.) den Hartog in Chile. Aquat Bot 15:195-200.
Smith TM, York PH, Broitman BR, et al. 2018. Rare long-distance dispersal of a marine angiosperm across the Pacific Ocean. Global Ecol Biogeogr 27:487-496.
Smith TM, York PH, Keough MJ, et al. 2016. Spatial variation in reproductive effort of a Southern Australian seagrass. Marine and Freshwater Research 120:214-224.
Thomson ACG, York PH, Smith TM, et al. 2015. Seagrass viviparous propagules as a potential long-distance dispersal mechanism. Estuaries and Coasts 38:927–940.
Seagrass Project Fondecyt 1231236