Journal of Environmental and Toxicological Studies ISSN 2576-6430 | Open Access SciO p Forschene n HUB for Sc i e n t i f i c R e s e a r c h RESEARCH ARTICLE Volume 3 - Issue 1 | DOI: http://dx.doi.org/10.16966/2576-6430.116 Fewer Species but More Existing Individuals: Testing the Hypothesis ‘Pessimum Conditions Rule’ Based on Long-Term Data of Species Composition of Benthic Fauna and Environmental Variables in the Sea of Marmara, Turkey M Levent Artüz1, O Bülent Artüz1, Mehmet Sakınç2, Bahattin Yalçın3* and B Eygi Erdoğan4 1Sevinç-Erdal İnönü Foundation, MAREM (Marmara Environmental Monitoring Project) Department of Marine Sciences, Anadoluhisarı Toplarönü, Istanbul, Turkey. 2Istanbul Technical University, Eurasia Institute of Earth Sciences, Istanbul, Turkey 3Department of Chemistry, Faculty of Science and Arts, Marmara University, Göztepe, Istanbul, Turkey 4Department of Statistics, Faculty of Science and Arts, Marmara University, Göztepe, Istanbul, Turkey *Corresponding author: Bahattin Yalçın, Department of Chemistry, Faculty of Science and Arts, Marmara University, Göztepe, 34722 Istanbul, Turkey, E-mail: [email protected] Received: 31 Aug, 2018 | Accepted: 01 Oct, 2018 | Published: 08 Oct, 2018 Citation: Artüz ML, Artüz OB, Sakınç M, Yalçın B, Erdoğan BE (2018) Fewer Species but More Existing Individuals: Testing the Hypothesis ‘Pessimum Conditions Rule’ Based on Long-Term Data of Species Composition of Benthic Fauna and Environmental Variables in the Sea of Marmara, Turkey. J Environ Toxicol Stud 3(1): dx.doi.org/10.16966/2576-6430.116 Copyright: © 2018 Artüz ML, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract The aim of this study is to try to prove the hypothesis that “When species diversity reduced, the survived unit members in the environment would be increased”, which named by us as “Pessimum conditions rule” in the scale of the Sea of Marmara. To prove the hypothesis “Pessimum conditions rule”, data from 604 observations both of benthic and oceanographically stations gathered in a 7-year period (2006-2012) were analyzed and compared, and the results used to show the relationship between classic biotic descriptors (e.g. number of species, number of individuals, richness index, dominance index, Shannon/Menhinick diversities) and environmental variables (e.g. Dissolved Oxygen, temperature, Salinity, pH) and depth. Multiple analysis of covariance and multiple linear regressions were used for the statistical analysis of the data. Correlations between benthic community indices and water quality variables showed that generally might affect community diversity. Besides this, it is clear that variation within benthic habitats in the Sea of Marmara cannot be explained by a single factor, such as uncontrolled overfishing and the revolving changes in the adjacent connected seas or driven by biotic interactions rather than by the water quality. According to the sample composition of benthic catches and related frequency values, a relative increase in the number of individuals was observed. This is also apparent by the correlation between basic pollution parameters and the community index values regarding long-term data of the present work. The measured values of the constant environment, created due to the unique structure of the Mediterranean originated lower layer of the Sea of Marmara, and correlated biotic parameters were showing a coherent dispersion in the completely sampling period. However, contrary to this, the values of the number of species were exactly the opposite. In the present study, pessimum conditions rule has been especially distinctive in the Sea of Marmara regarding the long-term data of the benthic catches. Also, this work report on species composition of the benthic catches in the Sea of Marmara for an assessment of the status of these communities and relation these communities with pollution phenomenon. Keywords: Diversity; Fauna; New records; Dominance; Species richness; Pessimum rule; Long-term monitoring Introduction In an inland sea, such as the Sea of Marmara, especially the coastal urban areas are subject to unfavorable ecological changes Anthropogenic impact on marine life has escalated over the last mainly associated with eutrophication, oxygen deficiency, semi centennial and threatened the balance of the ecosystem. Radical contaminants and overfishing. The unique water mass of Sea ecological changes in a sea can be provided most effectively by of Marmara has been strongly influenced by anthropogenic monitoring the benthic fauna, as most of the ecological impact and activities. pollution load ultimately will end up on the seabed. J Env Toxicol Stud | JETS 1 Journal of Environmental and Toxicological Studies SciO p Forschene n HUB for Sc i e n t i f i c R e s e a r c h Open Access Journal Sea of marmara Ünsal (1988), Balkıs (1992), Eryılmaz (1997), Uysal et al., (2002), Artüz et al., (2007, 2008, 2009,2011a, 2011b, 2012, 2013) [3,4,9-21]. In The entire system of Turkish Straits and Sea of Marmara extends addition to benthic studies, there were some specific works that partly from the Black Sea to the Aegean Sea through Bosporus (31 km), Sea discussed the benthic fauna of the Sea of Marmara and Turkish Strait of Marmara (210 km), and Dardanelles (60 km). The total length of System [22-31]. Biodiversity studies were very limited and inadequate the system is approximately 300 km, with a maximum depth of 1273 for studying this unique water mass, which was considered as a m. The maximum depth of the Sea of Marmara is controversial. The passageway or biological corridor. most accurate data are obtained by IFREMER [1] during earthquake studies, with a maximum of 1273 m. Over the years, the Sea of Marmara has been under pressure in terms of pollution from domestic and industrial wastewater sources. Because of the combination of precipitation and runoff exceeds Therefore, water quality has degraded significantly and biodiversity evaporation, relative low salinity and less dense water mass of the has been compromised in the Sea of Marmara. The current study Black Sea is entirely different from those of the Mediterranean Sea presents literality of the pollution-based theory “When species originated saline and correspondingly dense water mass [2]. Due to diversity reduced, the survived unit members in the environment the great differences in salinity-based density between the waters of would be increased” for Sea of Marmara, that first proposed by Artüz, the Black Sea and the Mediterranean Sea, there is a two-layered current et al, 2007 regarding long-term data between years 2006 and 2012. system along the Turkish Straits and the Sea of Marmara, flowing in opposite directions [3]. In addition, there are serious vertical mixing Materials and Methods points along those waterways especially in narrow and shallow straits and it tends to reduce the density of the deeper surface layer (approx. Rationale 200 m). Therefore, the deeper surface layer of the Sea of Marmara has In this study, Sea of Marmara is particularly selected as an a lower density than that of the water in the Aegean Sea at the equal appropriate model to test the “Pessimum conditions rule” because depth [4]. of providing the following conditions; i) presence of long-term and As the connection between the Mediterranean Sea via Dardanelles regular benthic and chemical-physical oceanographic data; ii) the and the Black Sea via Bosporus, the Sea of Marmara is a two-layered sub-thermocline water mass carrying the Mediterranean water water mass with unique circumstances and attributes that determine mass properties, particularly; iii) is relatively small in size and easily its biological and ecological characteristics. The Sea of Marmara controllable in terms of pollution parameters; iv) as a suitable model for testing the hypothesis that species are biologically close to the is situated between these two different ecosystems and serves as Mediterranean in terms of diversity. a sheltering, feeding and nesting area for both the Mediterranean Sea and the Black Sea originated forms, constituting a biological Study area and location of sampling stations corridor [3]. A series of samples were taken at annually at periodic intervals Collectively, the two Straits and the Sea of Marmara provide an at same localities in Sea of Marmara from August 2006 to August important “acclimatization zone” for transiting species during their 2012. The study was conducted at 61 stations (Figure 1) in the Sea migration from the Black Sea to the Aegean Sea and vice versa [5]. In of Marmara, between 15/08/2006 and 30/07/2012 (Table 1). Locations addition, because of this, the increasing manner of Lessepsian invasion were determined by MAP 330GPS as part of the project MAREM began to strongly affect to the Sea of Marmara as a result of decreased (Marmara Environmental Monitoring Project) entitled, “Changing competition due to the reduction in species diversity [6]. Oceanographic Conditions of the Sea of Marmara”, Istanbul. Previous benthic studies in the Sea of Marmara Macrofauna sampling and sample processing The first benthic study on the Sea of Marmara was carried out by A twin beam trawler ‘Oktay 4’ (length overall, 28 m; gross tonnage, Ostroumoff, et al. [7,8]. Following benthic and biological studies were 142 GT; main engine, 735 kW) was used for the study. The vessel was by Marion (1898), Demir (1954), Tortonese (1959), Caspers (1968), rigged for twin 3,75 m beam trawls with 18 and 3,6 mm stretched Figure 1: Survey area map of the MAREM (Marmara Environmental Monitoring) project, showing the 10 fixed beam-trawl sampling stations (▼) for each year. Citation: Artüz ML, Artüz OB, Sakınç M, Yalçın B, Erdoğan BE (2018) Fewer Species but More Existing Individuals: Testing the Hypothesis ‘Pessimum Conditions Rule’ Based on Long-Term Data of Species Composition of Benthic Fauna and Environmental Variables in the Sea 2 of Marmara, Turkey.