66 Relationship between viable cell transport of the diatom Didymosphenia geminata and other invasive species in Tierra del Fuego Island, Chile Marco Pinto1, 2, 3*, Máximo Frangópulos2, 3, 5, Sebastián Ruiz4, 7 and Carla Mora6 1
Escuela de Graduados, Instituto de Acuicultura Universidad de Chile, sede Puerto Montt, Balneario Pelluco S/N, Puerto Montt, Chile. *
[email protected]. 2Centro Regional Fundación CEQUA, Avenida España 184, Punta Arenas, Chile. 3Centro FONDAP de Investigación en Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Av. El Bosque 01789, Punta Arenas, Chile. 4Universidad de Valparaíso, Facultad de Ciencias de Mar y Recursos Naturales. Av. Borgoño 16344, Viña del Mar, Concón, Valparaíso, Chile. 5Universidad de Magallanes, Av. Bulnes 01855, Punta Arenas, Chile. 6Servicio Nacional de Pesca y Acuicultura, Departamento de Acuicultura, 21 de Mayo 1490, Punta Arenas Chile. 7Grupo de Estudios Ambientales, Instituto de la Patagonia, Avenida Bulnes 01890, Punta Arenas, Chile.
Abstract The Magellan region (southern Chile) has been aware of the introduction and spread of Invasive Alien Species (IAS). For decades, it has been exposed to the impact by species from Argentina, which arrived in 1946 with 25 pairs of beavers that were released in the north of Lake Fagnano, and in 1948 75 males and 155 females of muskrat were released in lentic systems of Tierra del Fuego island. The presence of IAS on the island has become even more complex with the detection in 2013 of the invasive microalga Didymosphenia geminata (Didymo) in two connected freshwaters sources, the Grande and Blanco rivers (in Chile and Argentina respectively). This study aims to explain the possible relationship between wildlife mobility and Didymo cell transport within the Grande river watershed, proposing beavers as a target species. A total of 10 individuals of the beaver Castor canadensis were collected and analysed. The presence of viable cells of Didymosphenia geminata was identified on different parts of the body of the individuals obtained. This finding suggests that IAS such as beavers can act as vectors for Didymo in Tierra del Fuego and wildlife should be considered in management strategies to limit the spreading of D. geminata from one watershed to another. Keywords: Didymosphenia geminata, invasive alien species, freshwater system, river Introduction The Magellan region (southern Chile) has been aware of the risk from introduction and spread of invasive alien species (IAS) (Simberloff, 2011). For decades, it has been exposed to the impact caused by several species from Argentina, which began in 1946 with 25 pairs of beavers, that were released in the north of Fagnano lake, and in 1948 a total of 75 males and 155 females of muskrat were released in various lentic systems of Tierra del Fuego Island (Jaksic et al., 2002). Both species, as well as mink, crossed the boundary that divides the two countries and spread throughout the entire Chilean Patagonian territory, causing negative impacts on the biodiversity of the Tierra del Fuego Archipelago (Sielfeld y Venegas, 1980; Rojel, 2009). The presence of IAS in the island has become even more complex with the detection in 2013 of the invasive microalga
Didymosphenia geminata (Lyngbye) Schmidt 1899 (Didymo) in two connected freshwaters sources, the Grande and Blanco rivers (in Chile and Argentina respectively) (Figure 1). Didymo is a very aggressive benthic diatom, capable of producing massive algal blooms, which can completely cover the benthic substrate of the watercourses that it affects, because of excessive production of extracellular stalks, which ends up causing severe physical, chemical and biological impacts on ecosystem processes (Kilroy, 2004; Blanco & Ector 2009; Whitton et al., 2009; Bishop & Spaulding, 2017) Both the Grande and Blanco rivers, have special hydric and limnological characteristics (Niemeyer, 1982), which allow to maintain stable ecosystems of Tierra del Fuego Island. They sustain a great diversity of habitats, and are the favorite locality for numerous native and invasive wildlife, which use water as a source for drink,
Proença, L. A. O. and Hallegraeff , G.M. (eds). Marine and Fresh-Water Harmful Algae. Proceedings of the 17th International Conference on Harmful Algae. International Society for the Study of Harmful Algae 2017.
67 shelter, breeding and feeding at several times per year (Schiavini & Raya-Rey, 2001). This study aims to explain the possible relationship between wildlife mobility and Didymo cell transport within the Grande river basin, using beavers as a target species that act as a vector of viable Didymo cells from one freshwater source to another. Simultaneously we seek to explain the ecological relationship between Didymo transport and propagation upstream of the Grande river basin. Material and Methods
A total of 10 individuals of the beaver Castor canadensis were collected between the Grande river and Blanco lake in Tierra del Fuego, using a Conibear 330 trap, with a high degree of efficiency (Lizarralde et al., 1996). One of its main advantages is that it captures animals without changing the natural state of the sample site, minimizing loss and favoring the recolonization of fur. Trapping was performed under international standards of hunting, which avoids unnecessary suffering of animals and protects the safety of people (Lizarralde & Elisetch, 2002).
Sampling
Fig. 1. Monitoring stations at the Tierra del Fuego Island areas with Didymo and beavers presence in the Grande and Blanco rivers and Blanco lake. The square shows the sampling stations.
68 Following this procedure, several body sections of each trapped animal were brushed (head, tail, and front and rear trunk limbs). The samples obtained were placed into 60 ml flask and then preserved using formalin 5%. Finally, each animal was weighted and their total length and length of each sampled body sections was measured. In the laboratory, we analysed each sample by counting and identifying the phytoplankton groups using an inverted microscope. Results and Discussion The presence of Didymosphenia geminata viable cells was detected on different parts of the body of the beavers, showing a zoochoric transport relationship by the beavers. Bus-Leone et al., (2014) found a similar result for minks (Neovison vison) from the Aysen region, where the presence of Didymo cells on different sections of the animal body was detected. Early information about zoochoric information in wildlife can be found in Atkinson (1972), which pointed out that both birds and mammals are potential vectors of invasive and colonizing species. Regarding the distribution of Didymo cells on different parts of the beaver’s body, the head part showed the presence of viable cells in almost 60% of the sampled specimens; for the abdomen and trunk section a total of 100% presence was obtained for all specimens. On the tail zone, 40% presence was observed, and for the front and back legs between 40 and 70% were found, respectively. Along with Didymo, many other species of benthic diatoms were observed on the beaver fur, particularly the genera Cocconeis, Encyonema, Fragilaria, Gomphonema, Navicula, Pinnularia and Tabellaria. According the descriptions associated with the proliferation of D. geminata in different water courses, these benthic diatoms correspond to well-known groups of species. It should be noted that in benthic sampling of rivers, the same patterns were observed in areas with Didymo. In the case of a beaver sampled from an area without Didymo (one specimen), only some diatom genera were detected, such as Gomphonema, Nitzschia, Fragilaria and Pinnularia. (Figure 2). Native animal species as well as invasive ones can be transporters of Didymo cells through the freshwater systems in Tierra del Fuego Island, but the differences in the hydrological characteristics (physical, chemical and biological) of this system can be a limiting factor for the establishment and
development of the microalgae. An example is that the Grande river contains a zone with abundance of Sphagnum moss (peat), which creates an anoxic (low concentration of nitrogen) and acid (pH values of 4-5) environment, with high level of sedimentation (Van Breemen, 1995) allowing patchy Didymo distribution through the river systems. Not all cells that are being transported have the same possibility to generate extensive epilithic mats in freshwater systems. This study is only the second work after Bus Leone et al., (2014) demonstrating that wildlife can act as vectors of Didymo propagation in the watersheds from southern Chile. Future work on biosecurity and control plans for the spreading of Didymo in Patagonia should therefore consider integrated management strategies for multiple invasive species. Beavers are only a vector for transport of the algae, and its effectiveness as a dispersing agent depends on the environmental conditions where Didymo proliferates massively in the basins that the beaver inhabits.
Fig. 2 Presence of Didymosphenia geminata and other diatoms genera obtained the beaver’s fur from the freshwater systems of Tierra del Fuego Island (Grande and Blanco rivers).
Acknowledgements Programa “Transferencia técnica para generar medidas de prevención y evitar el ingreso de la plaga didymo (Didymosphenia geminata) en la región de Magallanes y Antártica Chilena”. Cod. 4728-28-LP14. Supported by Subsecretaria de Pesca y Acuicultura and GORE Magallanes (FONDEMA 2014).
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