Changing zooplankton assemblage and increasing jellyfish abundance in the coastal waters of Bushehr–Delvar

The present investigation was performed to identify the impact effect of development and climate change on the zooplankton assemblage in coastal waters of Bushehr-Delvar region. Sampling was occurred seasonally at depths of less than 10 m using a Bongonet (100 µm) at 10 stations including Jophreh, Jalali, Dastak, Saretol, Helileh, Bandargah, Niroogah, Bushehr, Piazy and Delvar from the summer 2015 to the spring 2016. 40 Zooplanktoon groups belong to 8 Phyla were identified. Crustaceans were the most dominant zooplankton group with the average annual abundance of 37.66% of total zooplankton abundance. The total annual abundance of jellyfish including Salps, Cnidaria and Ctenophora was 16.11% which in comparison with the previous registered data indicated a significant increase over the last four decades in the region. The average annual abundance of zooplankton and Shannon-wiener diversity index were 10577.5±5512.69 /m3 and 2.44±0.218, respectively. The highest and the lowest density of zooplankton were found in Saretol and Delvar stations with the average amounts of 21250±13874/m3 and 4388±3075/m3, respectively. Also, the highest and the lowest density and diversity of zooplankton were observed in the summer and the winter, respectively. Correlation coefficient between the average temperature variation with zooplankton density and Shannon–wiener diversity variations were assessed 0.665 (P<0.34) and 0.91 (P<0.09), respectively. Comparing the results of the present study with the results of the previous investigations indicated that zooplankton assemblage in the coastal waters of Bushehr-Delvar region has been changed under the influence of various natural and human pressures including increased temperature and nutrients which resulted in increasing the density, reducing diversity and changing the species composition of zooplankton.

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