Aeolian dust and hydro-biological characteristics: Decoding dust storm impacts on phytoplankton in the northern Arabian Gulf.

Aeolian dust is an essential source of growth-limiting nutrients for marine phytoplankton. Despite being at the core of the Global Dust Belt, the response of the Arabian Gulf ecosystem to such atmospheric forcing is rarely documented. Here, the hydro-biological effect of mineral dust was studied in the northern Arabian Gulf (NAG) off Kuwait through monthly water sampling (December 2020 to December 2021), dust-storm follow-up sampling, and mineral dust and nutrient addition in-situ experiments. The multivariate analysis of oceanographic data revealed pronounced hydro-biological seasonality. The mineral dust deposition during two severe dust storm events in March and June 2021 showed a spatially varying effect of dust on coastal waters. The dust storms elevated the surface dissolved iron levels by several magnitudes, increased the dissolved inorganic nitrogen and phosphorous levels, changed their stoichiometry, and offset the hydrobiological seasonality. In the microcosms, dust input temporarily reduced phytoplankton phosphorous limitation in a dose-dependent manner when mesozooplankton (copepods) grazing was minimal. The microphytoplankton response to mineral dust inputs was comparable to that with nitrogen and phosphorous treatment. While Both treatments increased diatom size structure and biomass, the abundance of single-celled diatoms was comparatively higher in dust treatment. Multivariate analysis indicated that dust deposition alters the hydrographical properties of the surface ocean during dust storm events. The effects, though transient, were traceable for 3-16 days post-storm in coastal waters. The response of the summer phytoplankton to these changes, if delayed or muted, should be interpreted with caution given the summer water column stratification, the high nitrogen: phosphorous ratio and the low phosphorous solubility of aerosol dust, and the complex pelagic microbial food web interactions in the NAG. This study thus underlines the importance of a multivariate approach in documenting the ecological implications of Aeolian dust storms on marine environments closer to the dust source regions.

[A case of dural arteriovenous fistula associated with bilateral thalamic lesions].

We report a 51-year-old man with a dural arteriovenous fistula (DAVF) associated with bilateral thalamic lesions. He was admitted to our hospital because of cognitive disorder. T2-weighted MRI and fluid-attenuated inversion recovery (FLAIR) sequence of the brain revealed symmetric hyperintense lesions of bilateral thalamus and abnormal flow void that represents the enlarged veins. Cerebral angiography demonstrated DAVF in the superior petrosal sinus (SPS). It was mainly supplied by the internal carotid arteries. The strait sinus was not revealed, and the venous drainage was retrograde into the internal cerebral vein. Therefore the mechanism of cognitive disorder in this case was considered to be vasogenic edema of the bilateral thalamus due to DAVF of SPS. We decided to treat the DAVF by embolization via the feeding arteries approach, because strait sinus was not revealed and venous approach was difficult. After embolization, the size of DAVF was remarkably reduced. His cognitive disorder was markedly improved and the hyperintense area on T2-weighted MRI and FLAIR sequence had disappeared. Cognitive disorder due to DAVF of SPS is very rare. It is also difficult to diagnose bilateral thalamic lesions as DAVF, but it may be reversible by DAVF treatment. Thus, early diagnosis and treatment is important. Like this case, abnormal flow void that represents the enlarged veins could help to diagnose bilateral thalamic lesions due to DAVF.