Global climate has fluctuated greatly during the past three million years, leading to the recent major ice ages. An inescapable consequence for most living organisms is great changes in their distribution, which are expressed differently in boreal, temperate and tropical zones. Such range changes can be expected to have genetic consequences, and the advent of DNA technology provides most suitable markers to examine these. Several good data sets are now available, which provide tests of expectations, insights into species colonization and unexpected genetic subdivision and mixture of species. The genetic structure of human populations may be viewed in the same context. The present genetic structure of populations, species and communities has been mainly formed by Quaternary ice ages, and genetic, fossil and physical data combined can greatly help our understanding of how organisms were so affected.

http://webpages.icav.up.pt/PTDC/BIA-BEC/105083/2008/hewitt2000.pdf

The genetic legacy of the Quaternary ice ages

Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

Supporting Online Material for Spreading Dead Zones and Consequences for Marine Ecosystems

Estuarine and coastal transformation is as old as civilization yet has dramatically accelerated over the past 150 to 300 years. Reconstructed time lines, causes, and consequences of change in 12 once diverse and productive estuaries and coastal seas worldwide show similar patterns: Human impacts have depleted >90% of formerly important species, destroyed >65% of seagrass and wetland habitat, degraded water quality, and accelerated species invasions. Twentieth-century conservation efforts achieved partial recovery of upper trophic levels but have so far failed to restore former ecosystem structure and function. Our results provide detailed historical baselines and quantitative targets for ecosystem-based management and marine conservation.

/pdf/depletion-degradation-and-recovery-potential-of-estuaries-1hinljyave.pdf

Depletion, Degradation, and Recovery Potential of Estuaries and Coastal Seas

Population structure is the result of both present processes and past history. Molecular markers are proving of great value in describing the former, and it is important to similarly determine the latter in order to understand their respective contributions. The study of palaeo-climates has also advanced significantly, and in particular that of the Pleistocene ice ages, which modified species ranges considerably. The last ice age and rapid post-glacial colonization of Europe is summarized. Possible population genetic consequences of expansion northward from southern refugia, and those of remaining in these mountainous regions are discussed. A series of recent case studies are detailed where DNA sequence information has been used to describe species genetic variation and subdivision across Europe. These include a grasshopper, the hedgehog, oak trees, the common beech, the black alder, the brown bear, newts, shrews, water vole, silver fir and house mice. These molecular data confirm southern peninsulas of Europe as major ice age refugia, and in most cases demonstrate that genetically distinct taxa emerged from them. They can thus define genomic differences and so greatly augment previous fossil data. The refugial genomes contributed differently in various species to the re-colonization of Europe, with three broad patterns described as paradigms—«grasshopper», «hedgehog» and «bear». These different expansion patterns produced clusters of hybrid zones where they made contact, and it is argued that many species genomes may be further cryptically subdivided. A reduction in diversity from southern to northern Europe in the extent of allelic variation and species subdivision is seen; this is attributed to rapid expansion northward and the varied topography of southern refugia allowing populations to diverge through several ice ages. The differences in DNA sequence indicate that some species have been diverging in refugial regions for a few ice ages at most, whilst distinct lineages in other species suggest much more ancient separation.

https://www.fc.up.pt/mestr_biodiv/aulas/hewitt_1999.pdf

Post-glacial re-colonization of European biota

In marine ecosystems, rising atmospheric CO2 and climate change are associated with concurrent shifts in temperature, circulation, stratification, nutrient input, oxygen content, and ocean acidification, with potentially wideranging biological effects. Population-level shifts are occurring because of physiological intolerance to new environments, altered dispersal patterns, and changes in species interactions. Together with local climate-driven invasion and extinction, these processes result in altered community structure and diversity, including possible emergence of novel ecosystems. Impacts are particularly striking for the poles and the tropics, because of the sensitivity of polar ecosystems to sea-ice retreat and poleward species migrations as well as the sensitivity of coral-algal symbiosis to minor increases in temperature. Midlatitude upwelling systems, like the California Current, exhibit strong linkages between climate and species distributions, phenology, and demography. Aggregated effects may modify energy and material flows as well as biogeochemical cycles, eventually impacting the overall ecosystem functioning and services upon which people and societies depend.

/pdf/climate-change-impacts-on-marine-ecosystems-mu6opf56n1.pdf

Climate Change Impacts on Marine Ecosystems

The depth dependency of planktonic/benthic foraminiferal ratios: Constraints and applications

https://doc.rero.ch/record/29510/files/spe_fit.pdf

The FOBIMO (FOraminiferal BIo-MOnitoring) initiative—Towards a standardised protocol for soft-bottom benthic foraminiferal monitoring studies

The distribution and morphology of the benthic foraminifera in the Adriatic
Sea appear to be strongly dependent on two primary controlling environmental
parameters, oxygen concentration and food availability. These factors are both
governed by the runoff from the Po and other Italian rivers, and by the subsequent
distribution of the fluvial discharge products by the system of surface
currents.
The area most strongly influenced by runoff products, which is characterized
by ample food availability and low oxygen concentrations at the bottom, is a
strip parallel to the Italian coast at a water depth of between 20 and 60 m. In
the present study we describe in detail the changes in the benthic foraminiferal
faunas along transects perpendicular to this zone. The faunas along these
transects react essentially in two different ways to the changes in environmental
conditions. On the one hand we see qualitative and quantitative changes in the
composition of the faunas, and on the other hand a number of species show
a high degree of ecophenotypic variation.
Statistical analysis of the faunal patterns resulted in the recognition of eight
faunal clusters. One of these clusters, occurring in the near-shore zone, is consisting
of obviously reworked specimens. The other seven clusters are separated
on the basis of differences in the tolerances for stressed conditions and in the
preferences for particular feeding niches of the various taxa. In the centre of the
zone influenced by run-off products the faunas are dominated by a cluster with
Bulimina marginata forma denudata and Nonionella turgida. Obviously the
taxa of this cluster have the greatest tolerance for the sometimes stressed conditions
found in this area.
In the taxa Ammonia parkinsoniana, Elphidium granosum and Elphidium
poeyanum, comparable successions of three fundamental morphologies are
demonstrated. Compact morphotypes are typical for the near-shore, relatively
nutrient-poor and oxygen-rich environment, in which there is a minimum influence
of runoff products. In the somewhat deeper, food-enriched environment
with lower oxygen concentrations, inflated morphologies occur. Still
deeper, in the central part of the strip influenced by run-off products, where
oxygen-poor conditions occur, these types are found with supplementary
characteristics.
The study of the variation in Bulimina marginata suggests that in this taxon
the morphology reflects the life position of the animal. On the basis of the
distribution of different morphologies in this and in similar species, it is concluded
that the degree of niche separation in benthic foraminifera is dependent on the thickness of the oxygen-containing layer. If this thickness is minimal,
the inbenthic microhabitat is ruled out, and only taxa adapted to an epibenthic
microhabitat are found.
In the final chapter some possibilities to apply the results of our study are
discussed. It is argued that the bathymetrical distribution of benthic
foraminifera in the Adriatic Sea is largely influenced by variations in productivity.
Although the Recent situation can be described in great detail, one
should be careful about using these data for estimating paleo-depths in other
basins and/or other time-slices.
Far more promising is the potential use of the present results for the interpretation
of benthic foraminiferal faunas from deltaic environments in terms
of productivity. It is demonstrated that not only variations in the productivity
itself can be distilled, but also the source of such variations, such as variations
in run-off, changes in circulation patterns and sea level fluctuations. It is suggested
that benthic foraminifera should be used more often in pollution studies,
because they can provide an accurate description of the distribution patterns of
pollution phenomena in the bottom environments.

Frans Jorissen

Papers

The depth dependency of planktonic/benthic foraminiferal ratios: Constraints and applications

The FOBIMO (FOraminiferal BIo-MOnitoring) initiative—Towards a standardised protocol for soft-bottom benthic foraminiferal monitoring studies

Benthic foraminifera from the Adriatic Sea : principles of phenotypic variation

The distribution of benthic foraminifera in the Adriatic Sea

Vertical distribution of benthic foraminifera in the northern Adriatic Sea: The relation with the organic flux