Marine pockmarks are globally widespread seabed depressions, conventionally thought to be formed by the accumulation and expulsion of microbial and thermogenic gas. However, other putative fluids and processes have been implicated in pockmark formation and gas escape to the atmosphere may be underestimated. Given the complex spectrum of aquatic settings, morphologies and sizes, there may also exist a spectrum of physical, chemical and biological processes that form pockmarks. Pockmarks in shallow coastal waters are now understood to be widespread, but the influence of physical dynamics (e.g. tides, storms, etc.), terrestrial processes and anthropogenic activities add considerable spatiotemporal complexity and uncertainty to our understanding of these features. Here, we revisit a field of small (ca. 2 m diameter), shallow (<1 m depth) pockmarks in Dunmanus Bay, Ireland. The presence of muddy surface sediments overlying sand in the pockmarked area indicates that gas accumulation within fine-grained surface sediments contributes to formation of the features. Previous work indicates that CH₄ is an important seepage fluid in Dunmanus and neighbouring bays. However, based on evidence from multiple surveys, we observe considerable spatiotemporal complexity, and the transient nature of the gas within sediments points to the potential for fluids other than traditional microbial or thermogenic CH₄, migrating from sources tens to hundreds of metres below the seafloor. We observed atypical porewater profiles where millimolar concentrations of H₂S concentrations are observed in surface sediments in the absence of SO₄²⁻ depletion, together with NH₄⁺ build-up from ammonification of sedimentary organic matter. Archaeal methanogens, anaerobic methanotrophic archaea and SO₄^2--reducing Deltaproteobacteria co-occur in surface sediments in the pockmark field and NMR revealed the presence of non-competitive substrates for methanogens. We hypothesize that in-situ methanogenesis and production of other volatile metabolites besides CH₄ (e.g. CO₂, dimethyl disulfide) from microbial degradation of organic matter are potential gaseous fluids and could contribute to the formation of small pockmarks.

海洋麻点是全球范围内普遍存在的海床洼地，通常认为是由微生物和热气的积累和驱除形成的。但是，其他推测的流体和过程也与麻点形成有关，气体向大气的逸出可能会被低估。考虑到复杂的水生环境，形态和大小，可能还会存在形成麻子的一系列物理，化学和生物过程。现在，人们已经认识到浅海沿海地区的麻点很普遍，但是物理动力学（例如潮汐，风暴等），陆地过程和人为活动的影响为我们对这些特征的理解增加了相当大的时空复杂性和不确定性。在这里，我们将重新讨论小（直径约2 m），浅（< 爱尔兰Dunmanus湾的深度为1 m）的麻子。麻子状区域上覆盖着沙子的泥泞表面沉积物的存在表明，细粒表面沉积物中的气体蓄积有助于特征的形成。先前的工作表明CH₄是Dunmanus及其邻近海湾的重要渗流液。但是，基于多项调查的证据，我们观察到了相当大的时空复杂性，并且沉积物中气体的瞬态性质表明了从传统微生物或热源CH ₄以外的流体的潜能，这些流体从海底以下几十米到数百米的水源中迁移。 。我们观察到非典型孔隙水剖面，其中在没有SO ₄ ^2-耗竭的情况下，在表层沉积物中观察到毫摩尔浓度的H ₂ S浓度，以及由于沉积有机物的氨化而产生的NH ₄ ⁺堆积。古细菌产甲烷菌，厌氧甲烷营养古细菌和SO ₄pockmark场中的表面沉积物中同时发生^2-还原型Deltaproteobacteria细菌，NMR揭示了产甲烷菌的非竞争性底物的存在。我们推测在-原位甲烷生成和生产其它挥发性代谢物的除CH ₄（例如CO ₂，二甲基二硫化物）由有机物质微生物降解是潜在的气态流体，并可能有助于小麻子的形成。