The effects of decomposing invasive jellyfish on biogeochemical fluxes and microbial dynamics in an ultra-oligotrophic sea

Abstract

Abstract. Over the past several decades, jellyfish blooms have intensified spatially and temporally, affecting functions and services of ecosystems worldwide. At the demise of a bloom, an enormous amount of jellyfish biomass sinks to the seabed and decomposes. This process entails reciprocal microbial and biogeochemical changes, typically enriching the water column and seabed with large amounts of organic and inorganic nutrients. Jellyfish decomposition was hypothesized to be particularly important in nutrient-impoverished ecosystems, such as the Eastern Mediterranean Sea – one of the most oligotrophic marine regions in the world. Since the 1970s, this region has been experiencing the proliferation of a notorious invasive scyphozoan jellyfish, Rhopilema nomadica. In this study, we estimated the short-term decomposition effects of R. nomadica on nutrient dynamics at the sediment–water interface. Our results show that the degradation of R. nomadica has led to increased oxygen demand and acidification of overlying water as well as high rates of dissolved organic nitrogen and phosphate production. These conditions favored heterotrophic microbial activity and bacterial biomass accumulation, and triggered a shift towards heterotrophic biodegrading bacterial communities, whereas autotrophic picophytoplankton abundance was moderately affected or reduced. This shift may further decrease primary production in the water column of the Eastern Mediterranean Sea. Deoxygenation, acidification, nutrient enrichment, and microbial community shifts at the sediment–water interface may have a detrimental impact on macrobenthic communities. Based on these findings, we suggest that jelly-falls and their decay may facilitate an additional decline in ecosystem functions and services.

Bacterial Communities Associated With Four Blooming Scyphozoan Jellyfish: Potential Species-Specific Consequences for Marine Organisms and Humans Health

“…Note: Abbreviations: Au, A. coerulea from Jiaozhou Bay in Qingdao; Cy, C. nozakii from Jiaozhou Bay in Qingdao; Ne, N. nomurai from Shidao Bay in Rongcheng; Rh, R. esculentum from Shidao Bay in Rongcheng; QD, ambient seawater from Jiaozhou Bay in Qingdao; RC, ambient seawater from Shidao Bay in Rongcheng. Condon et al, 2011;Blanchet et al, 2015;Chelsky et al, 2015;Sweetman et al, 2016;Guy-Haim et al, 2020). The four scyphomedusae in this study (A. coerulea, C. nozakii, N. nomurai, and R. esculentum) can all reach considerable biomass in coastal waters of China during June to September (Dong et al, 2010(Dong et al, , 2014Zhang et al, 2012;Wang P.P.…”

“…Jellyfish are conspicuous marine zooplankton that play critical roles in the exchange of material and energy in marine ecosystems ( Riemann et al, 2006 ; Pitt et al, 2009 ; West et al, 2009 ; Condon et al, 2011 ; Blanchet et al, 2015 ; Chelsky et al, 2015 ; Sweetman et al, 2016 ; Guy-Haim et al, 2020 ). The four scyphomedusae in this study ( A. coerulea , C. nozakii , N. nomurai , and R. esculentum ) can all reach considerable biomass in coastal waters of China during June to September ( Dong et al, 2010 , 2014 ; Zhang et al, 2012 ; Wang P.P.…”

“…Blooming jellyfish may convert large amounts of carbon into gelatinous biomass, which may limit the transfer of carbon in the food web ( Condon and Steinberg, 2008 ; Sweetman et al, 2016 ). Organic and inorganic matters released by jellyfish could influence microbial nutrient cycling and alter microbial structure and function ( Riemann et al, 2006 ; Condon et al, 2011 ; Guy-Haim et al, 2020 ). Therefore, bacterial communities associated with the blooming cnidarian jellyfish were speculated to be major participants in the biogeochemical cycling of carbon, nitrogen, sulfur, and phosphorus ( Lee et al, 2018 ) and represent key vectors of potentially bacterial pathogens ( Ferguson et al, 2010 ; Schuett and Doepke, 2010 ; Delannoy et al, 2011 ; Basso et al, 2019 ; Clinton et al, 2020 ).…”

“…Jellyfish can stimulate bacterioplankton growth by direct release of nutrients from tissue, mucus secretion, excretion, and release of food particles when feeding ( Titelman et al, 2006 ; Pitt et al, 2009 ; Condon et al, 2012 ). Increased bacterial abundance has been observed in the vicinity of decaying jellyfish ( Titelman et al, 2006 ; Tinta et al, 2010 ; Blanchet et al, 2015 ; Guy-Haim et al, 2020 ; Tinta et al, 2020 ), such as the genera Vibrio and Pseudoalteromonas ( Tinta et al, 2012 ). However, even more importantly, growth of bacterioplankton surrounding live jellyfish may be stimulated by the release of nutrients and bioavailable carbon ( Titelman et al, 2006 ; Tinta et al, 2010 ; Condon et al, 2011 ).…”

The importance of jellyfish–microbe interactions for biogeochemical cycles in the ocean

“…For example, to study jellyfish decay rates, jellyfish are commonly isolated in a net, bag or bottle together with ambient seawater in a setup that allows for colonization of both microbes and larger organisms (i.e., mesh size of 5–10 mm; Titelman et al 2006) or using ambient seawater potentially containing organisms other than microbes (West et al, 2009; Frost et al, 2012). Also, some studies focused solely on the degradation of jellyfish biomass at the sediment surface (West et al, 2009; Chelsky et al 2016; Sweetman et al, 2016; (Guy‐Haim et al 2020), while others focused on the degradation process in the water column (Titelman et al, 2006; Tinta et al, 2010, 2012, 2016, 2020).…”