Biodiversity and community structure of free-living marine nematodes from intertidal areas in the Persian Gulf

The Persian Gulf is a semi-enclosed marginal sea, connected to the Gulf of Oman through the Strait of Hormuz. About one third of the world’s oil is produced in this region. It is an important military, economic and political region due to its oil and gas resources and it is one of the most important waterways in the world. Moreover, the Persian Gulf is located in a subtropical, hyper-arid region with often extreme air temperatures, a high evaporation rate and hence a high water salinity. The Persian Gulf hosts a variety of marine habitats such as rocky shores, estuarine ecosystems, mangrove habitats, salt marshes, sandy beaches, mud flats and coral reefs. Intertidal mud flats and sandy beaches are among the most widespread coastal habitats in the area. Because of the intensive human exploitation, the Persian Gulf is considered as one of the world's most polluted bodies of water. In addition to often wide-ranging pollution from oil-related activities, industrialization, urbanization, local sewage discharges and the building of numerous piers and docks all pose potentially serious threats to the marine life in this strategic location. In this PhD study, focus is on the northeastern part of the Persian Gulf, specifically the area of Bandar Abbas, the capital city of the Hormuzgan province, which is situated in the southeast of Iran. In the Iranian part of the Persian Gulf, only biodiversity and distribution of macrobenthos taxa or assemblages in intertidal marine habitats have hitherto received some attention. The meiobenthos has remained a completely neglected component of the benthos. This PhD therefore provides the very first study on the free-living marine nematode assemblages in coastal habitats of the Persian Gulf. It thus contributes substantially to the knowledge of the coastal marine biodiversity in the Iranian part of the Persian Gulf. Since this is a pioneering study, we first investigate biodiversity of nematode assemblages with a focus on spatial patterns in relation to local (so non-overarching) point sources of pollution, asking the question whether in such a broadly stressed environment, local pollution sources would still have a measurable impact on nematode assemblages. For this purpose, we focus on four beaches, and within each beach location, we assign three stations at different distances from local point sources of pollution. We then repeat the same sampling design almost exactly one year later to get a first impression of the consistency of the obtained spatial patterns over time, more specifically year-to-year variability. Finally, we look into the population-genetic structure of the two most abundant nematode species across a somewhat broader stretch (52 km) of coastline with the aim of studying connectivity and gene flow between populations from beach locations at a scale at which in other population-genetic studies of coastal nematodes, significant structuring has regularly been observed. Since both nematode species studied here tend to occupy different depth layers of the sediment, we also tested the hypothesis that the surface-dwelling species would show a lesser population-genetic structuring compared to the real endobenthic species

Lack of population genetic structure in the marine nematodes Ptycholaimellus pandispiculatus and Terschellingia longicaudata in beaches of the Persian Gulf, Iran

We investigated genetic diversity and population genetic structure of two common benthic nematode species, Ptycholaimellus pandispiculatus and Terschellingia longicaudata, from sandy beaches in the area of Bandar Abbas (Iran), Persian Gulf. Based upon partial mitochondrial cytochrome oxidase c subunit 1 (COI) gene data, 17 and two haplotypes were found for P.pandispiculatus and Te.longicaudata, respectively. Analysis of molecular variance did not reveal a significant population genetic structure for either species. The absence of genetic structuring indicates substantial dispersal and gene flow in our study area. To assess the species structure of Te.longicaudata at a larger geographic scale, we compared 18S rDNA and COI sequences from Iran and the Scheldt Estuary in The Netherlands to ascertain whether they truly belong to the same species. Our data confirmed previous studies that Te.longicaudata likely constitutes a complex of multiple cryptic species, with one of these species having a (near) cosmopolitan distribution

Biodiversity and community structure of free-living marine nematodes from intertidal areas in the Persian Gulf

Public defense: 2017-03-13D

Effects of pollution on nematode assemblage structure and diversity on beaches of the northern Persian Gulf

This study is the first to present data on local (=beach) and gamma diversity of beach nematode assemblages from the Persian Gulf. We investigated four beaches near the city of Bandar Abbas, Iran. On each beach, we sampled three stations at 50-m intervals, with increasing distance from a local pollution source, mostly domestic sewage. A total of 39 genera from 17 families was recorded. This gamma diversity is low and suggests that the entire area experiences substantial stress. Five genera together comprised 75% of nematode abundance. There were significant differences in abundance as well as genus diversity between locations, but these did not unequivocally correlate with known drivers of benthic assemblage structure like sediment granulometry and hydrodynamics. The location exposed to the strongest local pollution input had the lowest nematode diversity and a very low abundance at the station nearest the pollution source. Distance from local pollution sources also significantly impacted genus diversity, but this pattern was only pronounced in two of the four beaches. Our data demonstrate that local sources of anthropogenic disturbance are a major driver of assemblage diversity and structure in this area, despite an overarching effect of natural (salinity, temperature) and anthropogenic stressors