Sea level variability in Gulf of Guinea from satellite altimetry.

Coastal zones with dense populations, low elevations and/or inadequate adaptive capacity are on the frontline of unprecedented impacts from climate change. The Gulf of Guinea (GoG), stretching from Liberia to Gabon, is in particular vulnerable to coastal flooding caused by local and/or climate-induced sea level rise. In this region, interannual to decadal coastal sea level changes remain poorly understood, mainly due to a lack of tide gauge stations. Here we use nearly three decades (1993-2021) of satellite altimetry data to study the link between the Equatorial Atlantic and coastal GoG sea level variability. The rate of mean sea level rise increased from 3.47 to 3.89 ± 0.10 mm/yr from the Equatorial oceanic domain to the GoG coastal area, with an acceleration of 0.094 ± 0.050 mm/yr2. This corresponds to a mean sea level rise of about 8.9 cm over the entire altimetry period, 1993-2021. We focus on the (extreme) warm/cold events that occur in both the GoG during Atlantic Niños, and along the Angola-Namibia coast during Benguela Niños. Both events are driven by remote forcing via equatorial Kelvin waves and local forcing by local winds, freshwater fluxes and currents intensifications. Analysis of altimetry-based sea level, sea surface temperature anomalies, 20 °C isotherm based PIRATA moorings, and the Argo-based steric and thermometric sea level allows us to follow the coastal trapped waves (CTWs) along the GoG, and its link with major events observed along the strong Equatorial Atlantic warmings in 2010, 2012, 2019 and 2021. Both 2019 and 2021 warming have been identified as the warmest event ever reported in this region during the last 40 years. A lag of 1 month is observed between equatorial and West African coastal trapped wave propagation. This observation may help to better anticipate and manage the effects of extreme events on local ecosystems, fisheries, and socio-economic activities along the affected coastlines. In order to enable informed decision-making and guarantee the resilience of coastal communities in the face of climate change, it emphasises the significance of ongoing study in this field.

Global scale analysis on the extent of river channel belts.

Rivers form channel belts that encompass the area of the river channel and its associated levees, bars, splays and overbank landforms. The channel belt is critical for understanding the physical river evolution through time, predicting river behavior and management of freshwater resources. To date, there is no global-scale, quantitative study of the extent of river channel belts. Here we show, based on a pattern recognition algorithm, the global surface area of channel belts at an approximate 1 km resolution is 30.5 × 105 km2, seven times larger than the extent of river channels. We find 52% of river channels associated with the channel belts have a multi-threaded planform with the remaining 48% being single-threaded by surface area. The global channel belt (GCB) datasets provide new methods for high-resolution global scale landform classifications and for incorporating the channel belt into flood mitigation, freshwater budgets, ecosystem accounting and biogeochemical analyses.

Leaving a plastic legacy: Current and future scenarios for mismanaged plastic waste in rivers.

Mismanaged plastic waste (MPW) entering the riverine environment is concerning, given that most plastic pollution never reaches the oceans, and it has a severe negative impact on terrestrial ecosystems. However, significant knowledge gaps on the storage and remobilization of MPW within different rivers over varying timescales remain. Here we analyze the exposure of river systems to MPW to better understand the sedimentary processes that control the legacy of plastic waste. Using a conservative approach, we estimate 0.8 million tonnes of MPW enter rivers annually in 2015, affecting an estimated 84 % of rivers by surface area, globally. By 2060, the amount of MPW input to rivers is expected to increase nearly 3-fold, however improved plastic waste strategies through better governance can decrease plastic pollution by up to 72 %. Currently, most plastic input occurs along anthropogenically modified rivers (49 %) yet these represent only 23 % of rivers by surface area. Another 17 % of MPW occur in free-flowing actively migrating meandering rivers that likely retain most plastic waste within sedimentary deposits, increasing retention times and likelihood of biochemical weathering. Active braided rivers receive less MPW (14 %), but higher water discharge will also increase fragmentation to form microplastics. Only 20 % of plastic pollution is found in non-migrating and free-flowing rivers; these have the highest probability of plastics remaining within the water column and being transferred downstream. This study demonstrates the spatial variability in MPW affecting different global river systems with different retention, fragmentation, and biochemical weathering rates of plastics. Targeted mitigation strategies and environmental risk assessments are needed at both international and national levels that consider river system dynamics.

Intestinal lymphocytic epithelioganglionitis: a unique combination of inflammation in bowel dysmotility: a histopathological and immunohistochemical analysis of 28 cases.

AIMS: Visceral inflammatory neuropathies are enteric disorders underlying various forms of bowel dysmotility. The aim was to analyse the microscopic characteristics of a unique combination of intraepithelial lymphocytosis and myenteric ganglioneuritis. METHODS AND RESULTS: Paraffin sections of full-thickness proximal jejunal biopsy specimens from 28 patients, with proven disorders of gastrointestinal motility, were analysed following conventional and immunohistochemical staining. Serial transversal and tangential sectioning visualized large myenteric plexus areas. Between 1993 and 2005, 28 patients with inflammatory neuropathy (25 female and three male) showed this combination of lymphocytic infiltration. Two of the patients also had coeliac disease. The mean number of intraepithelial CD3+ lymphocytes was 36 per 100 epithelial cells (range 27-68; upper normal limit 25 lymphocytes). There was myenteric ganglionitis of variable severity (mean 4.6 myenteric lymphocytes per ganglion; upper normal limit two lymphocytes) with cytotoxic T-cell predominance. Myenteric neurons showed signs of degeneration and an abnormal immunohistological pattern. Hyperplasia and hypertrophy of Cajal cells were observed. The longitudinal muscle layer was thickened in many cases. CONCLUSIONS: A subset of patients with gastrointestinal motility disorders exhibit the combination of intraepithelial lymphocytosis and myenteric ganglionitis in full thickness biopsy specimens of the small bowel. We suggest calling this entity 'intestinal lymphocytic epithelioganglionitis'.

Full-thickness biopsy of the jejunum reveals inflammation and enteric neuropathy in irritable bowel syndrome.

BACKGROUND & AIMS: Irritable bowel syndrome (IBS) is regarded as a functional bowel disorder. Few studies have looked for histopathologic changes in the gut and only then in biopsy specimens from intestinal mucosa. Because bowel function is governed mainly by nerve plexuses in the bowel wall, we have investigated full-thickness bowel biopsy specimens in patients with severe IBS. METHODS: We used a laparoscopy-assisted technique to obtain full-thickness biopsy specimens from the proximal jejunum. Tissue specimens were investigated with light microscopy using routine stainings and immunohistochemical techniques. Horizontal sectioning was done to visualize large areas of the myenteric plexus. Fifteen autopsy specimens were used as controls regarding the myenteric plexus. Colorectal adenoma controls with terminal ileum biopsy specimens and full-thickness jejunal biopsy specimens from patients with degenerative enteric neuropathy were used as control groups for intraepithelial lymphocyte counts. RESULTS: Ten patients (2 males, 8 females) were studied. In 9 patients, we found low-grade infiltration of lymphocytes in the myenteric plexus. Lymphocytes had peri- and intraganglionic location. The mean number of lymphocytes per ganglion ranged from 1.9 to 7.1 per patient, with an overall mean of 3.4. No intraganglionic lymphocytes were found in the control group and only a few periganglionic lymphocytes (mean, 0.2). Four patients had concomitant intraepithelial lymphocytosis. Neuron degeneration was evident in 6 of 9 patients with and 1 patient without ganglionic lymphocyte infiltration. CONCLUSIONS: Our findings indicate that inflammation and neuronal degeneration in the myenteric plexus are involved in the pathogenesis of IBS.