Abstract Documenting operational setbacks is essential for refining marine conservation strategies. We present the lessons learned from an experimental restoration trial of habitat-forming Cystoseira sensu lato species under intense grazing pressure in Gökova Bay, eastern Mediterannean Sea. Transplanted thalli placed inside protective PVC-and-metal mesh exclusion-cages exhibited rapid growth and recruitment. However, upon cage removal, invasive Siganus spp. entirely consumed the macroalgae within 48 h. Operational constraints included wave-induced cage deformation, mesh clogging, and temperature-driven donor mortality (ΔT = 3 °C). These practical reflections demonstrate that direct transplantation is ecologically unviable without prior mitigation of widespread biotic stressors.
Abstract Iron is a key component of many enzymes and thus helps set the magnitude of primary production and nitrogen fixation. Other trace metals have essential metabolic functions but probably play lesser roles relative to iron. Studies report that manganese can, in certain ocean provinces and during some seasons, play an influential role in regulating phytoplankton metabolism. Evidence is based on nutrient amendment in shipboard incubations or manganese/iron stoichiometric patterns in resupply from depth. Iron recycling underpins primary production in High Nutrient Low Chlorophyll regions over most of the year. In contrast, less is known about manganese recycling. Here we compare Southern Ocean iron and manganese recycling using combined approaches to construct an ecological stoichiometric framework of the epipelagic (0–200 m depth) ocean. Our findings point to important differences in the stoichiometry of resupply of iron versus manganese, with manganese likely more efficiently recycled and hence retained in the upper ocean. In particular, the export of iron-rich copepod faecal pellets drives less retentive recycling by the “ferrous wheel” relative to the “spinning manga”. Such preferential retention of recycled manganese may offset observed differences in the stoichiometric supply of new iron compared with manganese and contribute to observed patterns of iron versus manganese limitation in the Southern Ocean.
Abstract Calcification by coccolithophores represents a major biogeochemical process in the oceans. Calcification involves the formation of calcite coccoliths within a Golgi-derived compartment inside the cell. These are secreted to the cell surface where they form the coccosphere. Coccolithophore calcification is underpinned by membrane transport processes that deliver the inorganic carbon and calcium substrates from the external seawater to the site of calcification and by the removal of products, namely protons produced in the calcification reactions. Understanding these critical aspects of calcification will provide clearer insights into the responses of coccolithophores to chemical and physical conditions, both in terms of short-term acclimation and long-term adaptation to a changing ocean. In this review we consider these processes, their localization and the specific transporters likely to be involved. We also consider how transport processes are linked to structural aspects of the cell, providing specialized pathways for the substantial ion fluxes involved.
Abstract Planktoniella is a genus of marine diatoms currently comprising nine species, including the type species Planktoniella sol. The taxonomic history of Planktoniella muriformis has been controversial; it was originally described as Coenobiodiscus muriformis and later transferred to Planktoniella. Morphological and molecular studies indicate that this species is phylogenetically distant from the type species. In this study, we clarify the taxonomic position of P. muriformis using an integrative approach combining morphological and molecular evidence. Colonies consisted of approximately 135–200 cells embedded in an organic matrix, with valves exhibiting eccentric areolation, a marginal ring of fultoportulae, each bearing four satellite pores, and a single rimoportula. Phylogenetic analyses based on LSU rDNA sequences recovered Planktoniella as a well-supported monophyletic clade, while the two P. muriformis sequences clustered within a subclade of Thalassiosira, as sister lineage to T. angulata. Genetic distances showed that P. muriformis diverged by 10.2 % from P. sol and by 4.9 % from T. angulata, confirming its closer affinity to the latter. Morphological and molecular evidence support the transfer of P. muriformis to the genus Thalassiosira, resulting in the new combination Thalassiosira muriformis . However, this change underscores the need for a comprehensive taxonomic revision of Thalassiosira , which remains polyphyletic.
