Abstracts PA2

Global Change Impacts and Social-ecological Responses




Abstract 120

A global dataset of coastal permeability and other attributes

by Nils Moosdorf | Jarrid Tschaikowski

ZMT Bremen, CAU Kiel | ZMT Bremen


Coasts are distinct places where the terrestrial meets the marine realm. As linear features, coasts do not occupy a large area on earth but still affect a large part of it, particularly in island settings. In addition, coastal positions can change over time based on linear, cyclic processes (e.g., tides) and nonlinear events like an erosion event during a storm. Thus, the positions of coasts change with time, but also in a fractal way based on the observation scale.

Coasts are usually not the focus of datasets describing any of the two realms. Datasets representing land or ocean attributes often do not even cover the actual coastlines. However, since the attributes of coasts can control coastal environments, it is important to know the attributes of coasts (e.g., physical, like slope or ecological, like dominant ecosystems). The coast also mediates the flow of groundwater to the oceans. Knowledge of coastal permeability is paramount to understanding this flow along the more than 2 million kilometers of global coast.

We developed a global coastal permeability map that aims to represent the coastal permeability of the world’s coast in maximum 1-kilometer segments. The map divides coastal permeability into three distinct views: Permeability of the landward aquifer, the shoreline, and the shallow marine sediments. Extensive GIS-based work was conducted to merge several recent global datasets representing many coastal attributes into a global database. The coastline was classified into permeability configurations based on combining coastline attributes.

Based on the collected dataset, we know the character of the 2 million kilometers of global coasts, including their permeability. Additional attributes can easily be added based on the developed methodologies. We can use this knowledge to extrapolate regional findings or characterize environments and define similarities between different coastal locations.


Abstract 122

Physiological effects of combined ocean acidification and warming on asterinid starfish

by Munawar Khalil | Steve S. Doo | Marleen Stuhr | Hildegard Westphal

Leibniz Centre for Tropical Marine Research (ZMT), Fahrenheitstraße 6, 28359 Bremen, Germany | Leibniz Centre for Tropical Marine Research (ZMT), Fahrenheitstraße 6, 28359 Bremen, Germany | Leibniz Centre for Tropical Marine Research (ZMT), Fahrenheitstraße 6, 28359 Bremen, Germany | Leibniz Centre for Tropical Marine Research (ZMT), Fahrenheitstraße 6, 28359 Bremen, Germany

Understanding how marine ecosystems are impacted by environmental stressors relies on accurate predictions of species-specific responses (performances of marine organisms) to climate change. In this study, we assess the combined effects of elevated pCO2 and temperature on organismal mortality, metabolic rate, righting activity, and calcification rates of the tropical asterinid starfish Aquilonastra yairi. Adult specimens of A. yairi were acclimated at two temperature levels (27 °C and 32 °C) crossed with three pCO2 concentrations (455 µatm, 1052 µatm, and 2066 µatm) for 90 days. At the end of the 90-day incubation, mortality was not altered by temperature and pCO2 treatments. Elevated temperature alone increased metabolic rate, accelerated righting activity, and caused a decline in calcification rate. In contrast, elevated pCO2 concentration increased metabolic rate and reduced calcification rate but did not significantly affect the righting activity. These results demonstrate that temperature is the main driver regulating starfish physiology. However, the combination of high temperature and high pCO2 concentration shows nonlinear and potentially synergistic effects on organismal physiology (e.g., metabolic rate), whereby the high temperature benefits the starfish to cope with the adverse effect of high pCO2 concentration (low pH) on calcification and minimize skeletal dissolution. Our study implies that while the temperature is the most significant stressor associated with global change for asterinid starfish, interactive effects with pCO2 might raise physiological perturbations.


Keywords: tropical starfish, multiple stressors, mortality, righting behaviour, metabolism, calcification

Abstract 121

Global groundwater recharge assessment over the last two decades

by Sara Nazari | Nils Moosdorf 

Department for Biogeochemistry/Geology, Centre for Tropical Marine Research (ZMT), Bremen, Germany. | Department for Biogeochemistry/Geology, Centre for Tropical Marine Research (ZMT), Bremen, Germany.

Groundwater is the largest global liquid freshwater source and is vital for providing reliable water resources for growing water consumption. One of the most uncertain parts of our knowledge of the global scale hydrological cycle is global groundwater recharge. Yet, measuring groundwater recharge requires detailed knowledge of environmental parameters and is observation-intensive. Therefore, we developed a global groundwater recharge model to analyze global groundwater recharge.

The model is a global hydrology grid-based concept with a spatial resolution of 0.1°×0.1° and daily temporal resolution. It comprises three soil layers: topsoil, subsoil, and aquifer. It simulates the exchange between topsoil and atmosphere performed by meteorological variables, as well as surface runoff, topsoil recharge, soil layers water volume, subsoil recharge, capillary rise from the subsoil, and groundwater recharge.

With the implementation of the model from 2001 to 2020, each global basin’s groundwater recharge was calculated. It is estimated that the global average groundwater recharge is 150 mm a-1 varying from zero to 1260 mm a-1. Moreover, a linear regression was applied for the decades 2001-2010 and 2011-2020 to evaluate how recharge has changed. An increasing trend in groundwater recharge was found in 68% of the world’s basins in the period 2001 to 2010. For the period from 2011 to 2020, this percentage has decreased to 48%. Basins with declining recharge show the opposite trend, comprising 32% of the basins in the first period and 52% in the second.

These outputs provide insight into uneven global groundwater recharge spatial and temporal distributions and indicate that the groundwater recharge decline in recent years threatens more basins. In addition, the results can be used to identify the regions where groundwater resources are or will be at risk of unsustainability.

Abstract 116

Thermal resilience of Halobatrachus didactylus

by Juan Molina | Pedro Guerreiro | Andreas Kunzmann 


In a context of climate change, warming of the seas challenges most species of fish to adapt. Understanding how different species cope with these changes in their environments at individual level can shed light on how populations and ecosystems will be affected. Utilizing a set of respirometry and experimental designs, we studied the thermal -related limits for Halobatrachus didactylus, a coastal sedentary fish that lives in intertidal environments of north-east Atlantic. This species proved to be highly resistant to thermal stress ( CTmax: 34.82 +/- 0.66 ºC) and presented size-specific differences in its stress response to increasing water temperatures, with smaller individuals being more sensitive. The metrics obtained in this study prove H. didactylus is surprisingly resilient to acute environmental variations in temperature.

Abstract xxx

Precipitation resonance for an idealized model ITCZ

by Jan O. Haerter & Romain Fiévet

ZMT, WG Complexity and Climate | The French Aerospace Lab ONERA

Tropical convective rainfall is known to vary with the diurnal cycle, yet it is also influenced by large scale convergence. In a suite of idealized numerical experiments, we mimic Earth’s Hadley cell to probe the cross talk between oscillations in rainfall inherent to the large-scale circulation and the rainfall oscillation caused by the convective diurnal cycle. The model tropics are thereby caricatured by a doubly-periodic domain with spatially constant surface temperature 𝑇𝑆 in the ”zonal” direction but decreasing 𝑇𝑆 when moving ”meridionally” away from the equator. We contrast temporally constant 𝑇𝑆 with diurnally varying 𝑇𝑆. We find that the large scale circulation develops an intrinsic mode of oscillation with a period ∼ 𝐿𝑦 proportional to the meridional domain size 𝐿𝑦 — thus generally differing from the diurnal period of one day. Interestingly, the diurnal forcing by no means shapes the precipitation power spectrum. Rather, the intrinsic circulation period dominates the precipitation power spectrum precipitation for large and small domains. At intermediate domain sizes, where intrinsic frequencies approximately match the diurnal one, the diurnal period prevails, the intrinsic frequency suppressed, and the precipitation amplitude amplified. We explain the complex dynamics as a type of resonance using a highly simplified forced and kicked harmonic oscillator.
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