Practical Guide to Measuring Wetland Carbon Pools and Fluxes.

Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions. Supplementary Information: The online version contains supplementary material available at 10.1007/s13157-023-01722-2.

Correlates of Waterbody Characteristics and the Occurrence or Diversity of Larval Amphibians in Central Ontario, Canada.

Watershed acidification and poor water quality can deleteriously affect amphibian populations. Between 1990 and 2008, we sampled 333 small, permanent (inundated year round) waterbodies that drain forested areas in the Algoma, Muskoka and Sudbury regions of central Ontario, Canada to determine whether water chemistry parameters, fish presence, and waterbody area and depth predict amphibian presence or diversity. Amphibians were present in some low-pH waterbodies, contrasting earlier studies, and generally water chemistry was not a strong indicator of amphibian presence or diversity in central Ontario. We suspect that other biotic and abiotic factors have a stronger effect on amphibian presence, and that the relationships between chemical and physical attributes and amphibian presence are complex. Future research should focus on long-term habitat change in central Ontario waterbodies to determine how watershed degradation has affected amphibians.

The influence of avian biovectors on mercury speciation in a bog ecosystem.

Methylmercury (MeHg) is a neurotoxin and endocrine disruptor that bioaccumulates and biomagnifies through trophic levels, resulting in potentially hazardous concentrations. Although wetlands are known hotspots for mercury (Hg) methylation, the effects of avian biovectors on these processes are poorly understood. We examined Hg speciation and distribution in shallow groundwater and surface water from a raised-bog with over 30years of avian biovector (herring gulls Larus argentatus and great black-backed gulls Larus marinus) colonization and guano input. Compared to the reference site, the avian-impacted bog had elevated concentrations of total dissolved organic carbon (TOC), total Hg, MeHg, phosphate (PO43-), and other trace metals, notably Pb, As, Cd and Ni. Spatial interpolation showed that the densest area of gull nesting was co-located with areas that had the highest concentrations of PO43-, MeHg, As and Cd, but not total mercury (THg), and models suggested that Mn, PO43-, and dissolved TOC were strong predictors of MeHg. Our findings suggest that while these gulls may not be a significant source of Hg, the excess of PO43- (a well recognised component of guano) and the subsequent changes in water chemistry due to avian biovector subsidies may increase net Hg methylation.