The Effect of Environmental and Anthropogenic Conditions on Shaping the Host-Microbiome of the Breadcrumb Sponge Halichondria panicea

Abstract

Marine sponges are vital to marine ecosystems, offering crucial habitats and functions, with their microbiome significantly contributing to nutrient recycling, biogeochemical activity, and host defense. The impact of the surrounding environment on marine sponge microbiomes has not been thoroughly explored, particularly in coastal areas with high pollution levels. To fill this gap, the sponge Halichondria panicea was selected in this study as an ideal model for coastal sponges because it is highly abundant in coastal areas around the world. This thesis presents a field study of the impact of environmental, biological, seasonal, and anthropogenic factors on H. panicea. Over the course of a year (2022), samples of the H. panicea microbial community were collected from three locations in the north-east of England, with a variety of bathing water quality levels, according to the UK's Environment Agency. Sponge, seawater, and attached seaweed samples were collected from the three locations and sequenced using metabarcoding of the 16S rRNA gene. The study emphasises the significant role of the seasons and anthropogenic activities in shaping the sponge bacterial community by affecting both composition and diversity. It also explores the acquisition of bacterial communities by H. panicea from its surroundings, revealing a significant proportion of the sponge microbiome is shared with seaweed, highlighting the interconnectedness of marine organisms in coastal environments. Additionally, the research investigates the relationship between the sponge's two colour morphs and its microbial community, suggesting that the yellow morph may be indicative of a sponge subjected to a certain stress. The study also includes the ex-situ cultivation of H. panicea to study the effect of different antifouling paints, revealing the negative impact of biocidal antifouling paint on sponge survival. Overall, the results of the thesis illustrate the complex interplay between environmental stressors and bacterial communities of the sponge H. panicea in coastal areas.