Looks can be deceiving: contrasting temperature characteristics of two morphologically similar kelp species co-occurring in the Arctic

Two morphologically similar digitate kelp species, Laminaria digitata and Hedophyllum nigripes, co-occur along a shallow sublittoral depth gradient in the Arctic but, in contrast to L. digitata, very few ecophysiological data exist for H. nigripes. We investigated growth, survival, photosynthetic characteristics and carbon:nitrogen ratios of juvenile sporophytes, and recruitment and survival of gametophytes in genetically verified Arctic isolates of both species along temperature gradients (0–25 °C) over 14 days. Laminaria digitata gametophytes survived 23–24 °C, while sporophytes survived 21–22 °C. Hedophyllum nigripes had lower temperature affinities. Gametophytes survived 19–21 °C, while sporophytes survived 18 °C. Male gametophytes were more heat-tolerant than female gametophytes in both species. The pronounced cold adaption of H. nigripes compared to L. digitata also became apparent in different sporophyte growth optima (L. digitata: 15 °C; H. nigripes: 10 °C) and gametogenesis optima (L. digitata: 5–15 °C; H. nigripes: 0–10 °C). Higher carbon:nitrogen ratios in H. nigripes suggest an adaptation to nutrient poor Arctic conditions. The overall temperature performance of H. nigripes possibly restricts the species to Arctic–Sub-Arctic regions, while Arctic L. digitata behaved similarly to cold-temperate populations. Our data suggest that a future increase in seawater temperatures may hamper the success of H. nigripes and favour L. digitata in Arctic environments.

Composting To Inactivate Foodborne Pathogens for Crop Soil Application: A Review

ABSTRACT Compost is organic material that has been degraded into a nutrient-stabilized humus-like substance through intense microbial activity, which can provide essential plant nutrients (nitrogen, phosphorus) to aid in the growth of fruits and vegetables. Compost can be generated from animal waste feedstocks; these can contain human pathogens, which can be inactivated through the heat and microbial competition promoted during the composting process. Outbreaks of infections caused by bacterial pathogens such as Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on fruit and vegetable commodities consumed raw emphasize the importance of minimizing the risk of pathogenic contamination on produce commodities. This review article investigates factors that affect the reduction and survival of bacterial foodborne pathogens during the composting process. Interactions with indigenous microorganisms, carbon:nitrogen ratios, and temperature changes influence pathogen survival, growth, and persistence in finished compost. Understanding the mechanisms of pathogen survival during the composting process and mechanisms that reduce pathogen populations can minimize the risk of pathogen contamination in the cultivation of fruits and vegetables.

Seston Ecology of the Surface Waters of Hudson Bay

The planktonic biomass variables, chlorophyll a, ATP, particulate organic carbon, and nitrogen have been measured in surface waters throughout Hudson Bay for the first time. On the basis of these variables Hudson Bay can be regarded as oligotrophc during the summer months. Clear inshore–offshore gradients of biomass were evident showing significant correlations in transects to salinity, temperature, depth, and distance from shore. Chlorophyll a values were always low, averaging 0.09 mg m−3 offshore and 0.28 mg m−3 inshore. ATP averaged 0.072 mg m−3 offshore and twice as high inshore. Biomass ratios also demonstrated clear inshore–offshore gradients; carbon:nitrogen ratios ranged from 4.9:1 inshore to 12.5:1 offshore indicating nitrogen limitation of offshore waters. Chlorophyll a: phaeopigment ratios decreased and biocarbon:chlorophyll a ratios increased offshore indicating an increased proportion of heterotrophs and possibly higher relative grazing pressure offshore. For the inshore areas, biomass and probably productivity were highest and significantly correlated to runoff with the exception of the Southampton–Coats–Mansel islands area, which is influenced by waters from Foxe Channel and Hudson Strait. While Hudson Bay meets most of the criteria for arctic classification, its character is sufficiently different to warrant special status.Key words: Hudson Bay, seston ecology, chlorophyll a, biomass ratios, phaeopigments, plankton