The planktonic ciliate community and its relationship with the environmental conditions and water quality in two bays of the Beagle Channel, Argentina

Abstract

The relationship between the ciliate community and the environmental variables in Ushuaia and Golondrina bays (54879 ′ S 68822 ′ W and 54885 ′ S 68836 ′ W, respectively) in the Beagle Channel, Argentina was investigated. The study was performed in three zones within the bays, previously delimited on the basis of their water quality. The most perturbed sites were located inshore. In order to analyse the contribution of each species to the similarity or dissimilarity between zones, similarity percentages analysis was undertaken using the Bray -Curtis similarity index. The variations in species composition and dominance in the selected zones were examined by the abundance-biomass comparison plot. We also studied the relationship between environmental and ciliates variability. The ciliate community comprised a total of 43 species belonging to 15 genera. Ciliate abundance and biomass varied temporally and spatially. A more diverse community dominated by small and opportunistic species tolerant to environmental changes was found in the most perturbed zone, while in the less stressed zone the community comprised bigger species, probably adapted to more stable environmental conditions. A community comprising species from both zones was found in a transitional area. We conclude that the structure of the community varied closely with environmental conditions.

Population structure and maturity stages of Fritillaria borealis (Appendicularia, Tunicata): seasonal cycle in Ushuaia Bay (Beagle Channel)

“…The mismatch found in the population structures and in the patterns of density of F. borealis between coastal and external sites could suggest the presence of two discernible subpopulations associated with the environmental characteristics of each zone, the coastal and the external ones. This hypothesis is coherent with the findings of BIANCALANA et al (2012BIANCALANA et al ( , 2014 and BARRÍA DE CAO et al (2013) who have shown the presence of different mesozooplanktonic and microzooplanktonic associations in the coastal and external zones of Ushuaia Bay. Also, due to the low depths, the presence of dense forests of macroalgae (Macrocystis pyrifera) in the coastal zone may contribute to the retention of zooplankton in this area.…”

Microzooplankton community structure in a subtropical South-West Atlantic coastal site

“…A total of 24 samples were collected representing 12 dates and two depths. Microzooplankton was identified to the lowest possible taxonomic level (i.e., species or genus level, whenever possible) based on morphological characteristics using bibliographic sources and taxonomic keys (e.g., Balech, 1988;Montagnes and Lynn, 1991;Barría de Cao, 1992;Lynn and Small, 2002). A special focus was made on dinoflagellates since they represent the most abundant group in the study area, and on ciliates (both, loricate and aloricate) as their study remains elusive.…”

“…Such studies suggested that water masses dramatically influence trophic dynamics by favouring the development of distinct plankton assemblages that may impact the top-down control of microzooplankton communities. Knowledge of regional microzooplankton derives from investigations further south in Argentinean waters (Thompson et al, 1999;Thompson and Alder, 2005;Santoferrara and Alder, 2009), including the Patagonian shelf (Antacli et al, 2018), the Beagle Channel (Barría de Cao et al, 2013) and the Bahía Blanca estuary (Barría de Cao et al, 2005Cao et al, , 2011Pettigrosso and Popovich, 2009;López-Abbate et al, 2015. Further observations are available for Brazilian coastal and shelf waters (Eskinazi-Sant' Anna and Björnberg, 2006;Islabão and Odebrecht, 2011;Gonçalves-Araujo et al, 2018;Menezes et al, 2019), and Patos Lagoon estuary (Jesus and Odebrecht, 2002).…”

Microbial plankton configuration in the epipelagic realm from the Beagle Channel to the Burdwood Bank, a Marine Protected Area in Sub-Antarctic waters

“…Local and regional references (e.g. [47,48,25]) as well as general literature of plankton taxonomy (e.g. [61,62]) were consulted.…”

“…Further, the area provides spawning and nursery habitat for important commercial fish species, such as the Patagonian sprat (Sprattus fuegensis) and the Patagonian toothfish (Dissostichus eleginoides) [44,45,46]. Nevertheless, few studies on phytoplankton [47,34] and microzooplankton [48] exist for the BC and even less offshore towards open oligotrophic waters [49], and none above the BB. Along the transition from the BC to the BB, complex hydrographical processes result from the convergence of different water masses and the irregular bathymetry [50,36], that lead to contrasting sub-regions likely inhabited by different plankton assemblages.…”