Assessment of the quality and quantity of organic matter in the Rufiji mangrove surface sediments using biochemical composition

This study was carried out to investigate spatial changes in the quality and quantity of sedimentary organic matter in the Rufiji mangrove system, Tanzania. Sediment samples were collected from three sampling sites. Total organic matter in mangrove sediments ranged from 7.28 ± 2.02% to 10.58 ± 1.34%. Protein concentrations varied from 1,145.33 ± 20.33 μg/g to 2,747.50 ± 25.14 μg/g in the mangrove sediments. Total carbohydrates, lipids and biopolymeric carbon in mangrove sediments ranged between 1,110.50 ± 16.31 μg/g and 1,914.17 ± 27.79 μg/g, 1,436.50 ± 24.13 μg/g and 6,373.50 ± 25.79 μg/g, and 4,496 μg C/g and 10,231.50 μg C/g, respectively. Tannins and lignins in mangrove sediments varied from 817.67 ± 12.97 μg/g to 1786.50 ± 30.74 μg/g, while stable carbon isotope (δ13C) in Rufiji mangrove sediments ranged between –26.64 ± 0.10 ‰ and –25.48 ± 0.13 ‰. Higher protein:carbohydrate (PRT:CHO) at station 3 indicated the presence of freshly deposited organic matter. The high lipid:carbohydrate (LPD:CHO) ratios observed in the Rufiji mangrove systems pointed towards the high quality of labile organic matter which supports benthic fauna. PCA revealed the association of variables and their distribution on trends across sites of the Rufiji mangrove system. Keywords: Organic matter, biochemical composition, Rufiji, mangroves, sediments

Anthropogenic nutrient loads and season variability drive high atmospheric N2O fluxes in a fragmented mangrove system

Fragmented mangroves are generally ignored in N2O flux studies. Here we report observations over the course of a year from the Mangalavanam coastal wetland in Southern India. The wetland is a fragmented mangrove stand close to a large urban centre with high anthropogenic nitrogen inputs. The study found the wetland was a net source of N2O to the atmosphere with fluxes ranging between 17.5 to 117.9 µmol m−2 day−1 which equated to high N2O saturations of between 697 and 1794%. The average dissolved inorganic nitrogen inputs (80.1 ± 18.1 µmol L−1) and N2O emissions (59.2 ± 30.0 µmol m−2 day−1) were highest during the monsoon season when the rainfall and associated river water inputs and terrestrial runoff were highest. The variation in N2O dynamics was shown to be driven by the changes in rainfall, water column depth, salinity, dissolved oxygen, carbon, and substrate nitrogen. The study suggests that fragmented/minor mangrove ecosystems subject to high human nutrient inputs may be a significant component of the global N2O budget.

Factors influencing spatial patterns in primary productivity in Kenyan territorial waters

This study was formulated to investigate productivity systems within Kenyan territorial waters. The interaction of processes on the margins of the marine waters, particularly the influx of fresh water loaded with sediments and nutrients, influences productivity of coastal waters. These deposited sediments, rich in nutrients, create a topographic barrier to the northerly flowing East African Coastal Current (EACC). Phosphate and nitrate peaks observed around the North Kenya Bank area provide evidence of an upwelling event. The contribution of sediments from the Lamu archipelago mangrove system is evident from the high observed particulate organic carbon (POC) input around the area. The system around the Lamu archipelago did not however show high chlorophyll-a levels despite the high POC influx. This may be due to the low levels of limiting phosphate in the surrounding waters, contrary to the observation further north in the region where high chlorophyll-a levels and corresponding higher phosphate levels were apparent. Productivity was largely supported by upwelling and organic matter mineralization. High levels of chlorophyll corresponded to high pelagic fish densities in the south (around 4.5°S) and north of the study area (around 2.5°S).

The Cost for Biodiversity: Records of Ciliate–Nematode Epibiosis with the Description of Three New Suctorian Species

Epibiosis is a common phenomenon in marine systems. In marine environments, ciliates are among the most common organisms adopting an epibiotic habitus and nematodes have been frequently reported as their basibionts. In the present study, we report several new records of peritrich and suctorian ciliates-nematode association worldwide: from a deep-sea pockmark field in the NW Madagascar margin (Indian Ocean), from a shallow vent area in the Gulf of Naples (Mediterranean, Tyrrhenian Sea), in a MPA area in the Gulf of Trieste (Mediterranean, Adriatic Sea), from a mangrove system in French Guiana (South America, Atlantic Ocean), and from the Maldivian Archipelago. In addition, three new species of Suctorea from the Secca delle Fumose shallow vent area (Gulf of Naples) were described: Loricophrya susannae n. sp., Thecacineta fumosae n. sp. and Acinetopsis lynni n. sp. In the light of these new records and data from the existing literature, we discuss the suctorian–nematode epibiosis relationship as a lever to biodiversity.