Characteristics of settling matter and its role in nutrient cycles in a deep oligotrophic lake

Shade-grown coffee is an important reservoir for tropical biodiversity, but habitat quality hinges on decisions made by farmers. Our research aims to investigate the link between coffee producers’ decisions and outcomes for biodiversity, using epiphytes as our focal group. Using qualitative methods, we interviewed 33 producers in northern Nicaragua to understand how they connect trees and epiphytes on their farms to ecosystem services and how personal values, access to agronomic expertise, labor supply, and financial stability influence decision-making. We used interview responses to construct six producer typologies. Most producers had strong positive attitudes toward trees and associated them with a variety of important ecosystem services. Smallholders were more likely to connect trees with provisioning services, while producers on larger farms and with greater agronomic knowledge emphasized regulating services. Most producers connected epiphytes primarily with aesthetic values. Across demographics, producers emphasized the restorative potential for shade coffee in repairing damage to soil, water, and nutrient cycles caused by other forms of agriculture. The conservation significance and sustainability of this social-ecological system can be maintained and expanded through economic and capacity-building conservation interventions, especially when those can be connected to values already held by farmers.

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Influences of environmental parameters and phytoplankton productivity on benthic invertebrates in a tropical oligotrophic lake, northern Malaysia

Environmental Science and Pollution Research ◽

10.1007/s11356-021-13671-6 ◽

2021 ◽

Author(s):

Mustafizur M. Rahman ◽

Ahmad Fathi ◽

Stephen R. Balcombe ◽

Bryan Nelson ◽

Akbar John

Keyword(s):

Benthic Invertebrates ◽

Environmental Parameters ◽

Oligotrophic Lake ◽

Phytoplankton Productivity

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Nitrogen removal processes in lakes of different trophic states from on-site measurements and historic data

Aquatic Sciences ◽

10.1007/s00027-021-00795-7 ◽

2021 ◽

Vol 83 (2) ◽

Author(s):

Beat Müller ◽

Raoul Thoma ◽

Kathrin B. L. Baumann ◽

Cameron M. Callbeck ◽

Carsten J. Schubert

Keyword(s):

Eutrophic Lake ◽

Oligotrophic Lake ◽

Removal Rates ◽

N Removal ◽

Central Switzerland ◽

Denitrification Activity ◽

Historic Data ◽

Anthropogenic Nitrogen ◽

Removal Processes ◽

Sediment Interface

AbstractFreshwater lakes are essential hotspots for the removal of excessive anthropogenic nitrogen (N) loads transported from the land to coastal oceans. The biogeochemical processes responsible for N removal, the corresponding transformation rates and overall removal efficiencies differ between lakes, however, it is unclear what the main controlling factors are. Here, we investigated the factors that moderate the rates of N removal under contrasting trophic states in two lakes located in central Switzerland. In the eutrophic Lake Baldegg and the oligotrophic Lake Sarnen, we specifically examined seasonal sediment porewater chemistry, organic matter sedimentation rates, as well as 33-year of historic water column data. We find that the eutrophic Lake Baldegg, which contributed to the removal of 20 ± 6.6 gN m−2 year−1, effectively removed two-thirds of the total areal N load. In stark contrast, the more oligotrophic Lake Sarnen contributed to 3.2 ± 4.2 gN m−2 year−1, and had removed only one-third of the areal N load. The historic dataset of the eutrophic lake revealed a close linkage between annual loads of dissolved N (DN) and removal rates (NRR = 0.63 × DN load) and a significant correlation of the concentration of bottom water nitrate and removal rates. We further show that the seasonal increase in N removal rates of the eutrophic lake correlated significantly with seasonal oxygen fluxes measured across the water–sediment interface (R2 = 0.75). We suggest that increasing oxygen enhances sediment mineralization and stimulates nitrification, indirectly enhancing denitrification activity.

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Macro- and Micronutrient Cycling and Crucial Linkages to Geochemical Processes in Mangrove Ecosystems

Journal of Marine Science and Engineering ◽

10.3390/jmse9050456 ◽

2021 ◽

Vol 9 (5) ◽

pp. 456

Author(s):

Daniel M. Alongi

Keyword(s):

Transformation Process ◽

Early Diagenesis ◽

P Availability ◽

Geochemical Processes ◽

Nutrient Cycles ◽

Physiological Mechanisms ◽

Retention Efficiency ◽

Mangrove Ecosystems ◽

N Metabolism ◽

Transformation Processes

High mangrove productivity is sustained by rapid utilization, high retention efficiency and maximum storage of nutrients in leaves, roots, and soils. Rapid microbial transformations and high mineralization efficiencies in tandem with physiological mechanisms conserve scarce nutrients. Macronutrient cycling is interlinked with micronutrient cycling; all nutrient cycles are linked closely to geochemical transformation processes. Mangroves can be N-, P-, Fe-, and Cu-limited; additions of Zn and Mo stimulate early growth until levels above pristine porewater concentrations induce toxicity. Limited nutrient availability is caused by sorption and retention onto iron oxides, clays, and sulfide minerals. Little N is exported as immobilization is the largest transformation process. Mn and S affect N metabolism and photosynthesis via early diagenesis and P availability is coupled to Fe-S redox oscillations. Fe is involved in nitrification, denitrification and anammox, and Mo is involved in NO3− reduction and N2-fixation. Soil Mg, K, Mn, Zn and Ni pool sizes decrease as mangrove primary productivity increases, suggesting increasing uptake and more rapid turnover than in less productive forests. Mangroves may be major contributors to oceanic Mn and Mo cycles, delivering 7.4–12.1 Gmol Mn a−1 to the ocean, which is greater than global riverine input. The global Mo import rate by mangroves corresponds to 15–120% of Mo supply to the oceanic Mo budget.

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