Oceanological and Hydrobiological Studies International Journal of Oceanography and Hydrobiology Volume 49, No. 2, June 2020 ISSN 1730-413X pages (123-131) eISSN 1897-3191 Use of rotifer trophic state indices to show the e ect of hydrobionts and nutrients on water trophic status in mesocosms by Abstract 1, We have determined how Crustacea, zebra mussels Jolanta Ejsmont-Karabin *, Irina (Dreissena polymorpha), fish and nutrients affect the trophic 2 Feniova , Iwona Kostrzewska- state in mesocosms filled with water collected from the Szlakowska3, Marek Rzepecki4, Varos G. pelagic zone of a eutrophic lake. We hypothesized that 2 5 the pool of nutrients would increase both directly due to Petrosyan , Andrew R. Dzialowski the input of phosphorus and nitrogen and/or indirectly due to the introduction of animal biomass. We used trophic state indices based on the abundance and species structure of rotifers to assess changes in the trophic state DOI: 10.1515/ohs-2020-0011 in mesocosms. The role of small detritophages in rotifer Category: Original research paper communities increased as a result of treatments. Our results clearly demonstrated that D. polymorpha was Received: August 19, 2019 able to reduce the trophic status of mesocosm waters Accepted: November 4, 2019 as indicated by reduced rotifer trophic state indices regardless of interactions with other treatment factors. Contrary to our expectations, neither the nutrients added 1Department of Hydrobiology Institute of Biology, at the beginning of the experiment nor the introduction of University of Białystok, ul. Świerkowa 20 B, 15-950, crustaceans or fish affected the rotifer trophic indices. Białystok, Poland 2A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninski Prospekt 33, Moscow, 119071, Russia 3Faculty of Biology, University of Warsaw, ul. Ilji Miecznikowa 1, 02-096 Warszawa, Poland 4Research Station in Mikołajki, Nencki Institute of Experimental Biology of Polish Academy of Sciences, ul. Ludwika Pasteura 3., 02-093 Warszawa, Poland 5Department of Integrative Biology, Oklahoma State Key words: Rotifera, eutrophic lake, e ects of University, 501 Life Sciences West, Stillwater, OK 74074 Dreissena’s, sh, Crustacea USA * Corresponding author: [email protected] The Oceanological and Hydrobiological Studies is online at www.oandhs.pl ©Faculty of Oceanography and Geography, University of Gdańsk, Poland. All rights reserved. 124 Oceanological and Hydrobiological Studies, VOL. 49, NO. 2 | JUNE 2020 Jolanta Ejsmont-Karabin, Irina Feniova, Iwona Kostrzewska-Szlakowska, Marek Rzepecki, Varos G. Petrosyan, Andrew R. Dzialowski Introduction the input of phosphorus and nitrogen or indirectly by the introduction of animal biomass. As a result, these Eutrophication is a process where the pool of inputs are expected to change the trophic state of nutrients in a lake increases as a result of an influx water in our experiment. However, the functioning of from outside the ecosystem. This increase in the pool invertebrate populations may also have an impact on of nutrients is then followed by changes in internal the trophic state. The nature of changes, especially in nutrient cycles (Ejsmont-Karabin 1983). Mineralization variants with D. polymorpha, fish and crustaceans, is of phosphorus (P) by heterotrophs generally provides difficult to predict. The main objective of this study a sufficient amount of P to sustain primary production was to assess the effect of adding different animal during periods of low P availability, but external pulses populations on the trophic state of lake waters. We are required to induce algal blooms (Kamarainen et al. used rotifers as indicators of trophic changes in the 2009). In eutrophic lakes, a smaller proportion of algal experiment as this group of zooplankton responds biomass is directly used by planktonic herbivores, concurrently to environmental changes due to their while a greater proportion is indirectly consumed high intrinsic growth rates (Beaver & Crisman 1990; (after cell death) by bacterivores. This may accelerate Ejsmont-Karabin 2012; Pociecha et al. 2018). the rate of nutrient regeneration (Ejsmont-Karabin 1983) and thus increase the pool of nutrients and the Materials and methods trophic state of lake waters in general. Experiments carried out by Bossard & Uehlinger (1993) have shown that the exclusion of crustaceans increases the The experiment was carried out from 31 July to 1 residence time of total P by a reduced P loss through September 2012 and consisted of 12 treatments, each sedimentation. Thus, the presence of crustaceans of which was replicated in triplicate mesocosms (36 should reduce the pool of phosphorus and, mesocosms in total). The outdoor mesocosms were consequently, the trophic state of waters. This role originally filled with 270 l of unfiltered water from of large cladocerans in the phytoplankton biomass the pelagic zone of eutrophic Lake Mikołajskie (498 control has been confirmed by Ejsmont-Karabin et ha; Masurian Lake District, northeastern Poland) and al. (2004), although in some cases other zooplankton kept on the shore of that lake during the experiment. organisms may play the same role. Mesocosms (plastic containers with internal Fish can affect the processes of eutrophication as dimensions of 0.94 m × 0.50 m, a height of 0.64 m and demonstrated by Stenson (1982). His manipulation of a capacity of 300 l) were devoid of sediments. fish at the top of the ecosystem resulted in changes in Three mesocosms were filled with unfiltered water nutrient cycles and the development of a new rotifer that contained the natural abundance of zooplankton community. A significant structuring role of fish was and served as the control (C). One-liter samples also shown in 8-year studies on three eutrophic lakes collected from each mesocosm were examined for (Jeppesen et al. 2000). Reduction in planktivores in the zooplankton on the day the experiment started. lakes resulted in an increase in cladoceran size and a According to the results of the observations, the decrease in chlorophyll a concentrations. control consisted of small cladocerans Chydorus Zebra mussels Dreissena polymorpha may also sphaericus (O.F. Müller), Bosmina coregoni Baird, play a quantitatively important role in the nutrient B. longirostris (O.F. Müller), Ceriodaphnia pulchella Sars budget of lakes (Goedkoop et al. 2011). They are and copepods Eudiaptomus gracilis Sars, E. graciloides expected to efficiently trap nutrients, thus it has been (Lilljeborg), Mesocyclops leuckarti (Claus), Thermocyclops proposed that they can be used to increase water oithonoides (Sars) and a community of rotifers strongly quality. In large-scale studies carried out in Saginaw dominated by species of the genus Polyarthra Bay (Fahnenstiel et al. 1995), D. polymorpha caused (P. remata Skorikov and P. vulgaris Carlin) and two a strong decrease in the trophic state of Saginaw species indicative of high trophic status: Anuraeopsis Bay (Lake Huron), i.e. a 59% and 43% decrease in fissa (Gosse) and Trichocerca pusilla (Lauterborn). chlorophyll a and total phosphorus, respectively, and The remaining treatments consisted of unfiltered a 60% increase in Secchi disk transparency. However, lake water plus: crustacean species (Cr), Dreissena D. polymorpha produces large quantities of detritus, polymorpha (Dp), nutrients (N), fish (F), Crustacea & which may also improve the trophic state of lake D. polymorpha (CrDp), fish & Crustacea (FCr), nutrients waters (Ejsmont-Karabin et al. 2004). & Crustacea (NCr), nutrients & D. polymorpha (NDp), In experiments on the impact of Crustacea, nutrients & fish (NF), nutrients & D. polymorpha & bivalves (Dreissena polymorpha), fish and nutrients, Crustacea (NDpCr), nutrients & fish & Crustacea (NFCr). the pool of nutrients was increased both directly by The Crustacea (Cr) treatment was a mixture of www.oandhs.ug.edu.pl ©Faculty of Oceanography and Geography, University of Gdańsk, Poland. All rights reserved. Oceanological and Hydrobiological Studies, VOL. 49, NO. 2 | JUNE 2020 125 Rotifer indices used to assess trophic state in mesocosms crustaceans: 500 ind. of Daphnia pulex (Leydig), 140 with a TSImean under 45 were mesotrophic, 45–55 were ind. of Simocephalus vetulus (O. F.Müller), and a few meso-eutrophic, 55–65 were eutrophic, and greater individuals of Macrocyclops albidus (Jurine) collected than 65 were hypertrophic (Ejsmont-Karabin 2012). from neighboring waterbodies and added to the We used a generalized linear model (GLM) for unfiltered lake water. These species were not present statistical analysis, which was designed to assess the in water from Lake Mikołajskie. effect of one or more treatment factors on one or Dreissena polymorpha individuals, which were more dependent variables. Our analyses involved scarce in Lake Mikołajskie, were transported in coolers three factors, including treatment (A), the number of from Lake Boczne to the field station. They were added mesocosms (B), and time, i.e. date (C). We analyzed to the mesocosms within 24 h of their collection. TSImean (averaged over all six TSI indices), TSIN based on −2 About 200 individuals of D. polymorpha (i.e. 250 g m ) the number of rotifers, TSIB based on rotifer biomass, were selected randomly from the common pool and TSIBAC based on the percentage of bacterivores in the introduced into each of the 12 mesocosms. total number of rotifers, TSIB/N based on the ratio of We enriched the water in six treatments (18 biomass to count. Two TSI indices (percentage