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Introduction
Current institution
Current position
- Professor Emeritus
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August 1986 - present
January 1986 - December 2020
Publications
Publications (191)
Reaching a deeper understanding of the ocean ecosystems that maintain whales might aid conservation efforts. Measurements of the animals’ krill intake indicate that previous figures were substantial underestimates. Whales in the ocean consume unexpectedly high levels of krill.
Multiple sources of evidence from past climate cycles clearly show a strong link between atmospheric CO2 concentrations, average global temperatures and sea level height. Rising sea levels will not only have a devastating effect on India’s coastal habitations and ecosystems but also on natural environments inland caused by pressure from coastal ref...
The genesis of phytoplankton blooms and the fate of their biomass in iron-limited, high-nutrient−low-chlorophyll regions can be studied under natural conditions with ocean iron fertilization (OIF) experiments. The Indo-German OIF experiment LOHAFEX was carried out over 40 d in late summer 2009 within the cold core of a mesoscale eddy in the product...
The LOHAFEX iron fertilization experiment was conducted for 39. days in the closed core of a cyclonic mesoscale eddy located along the Antarctic Polar Front in the Atlantic sector of the Southern Ocean. Mixed layer (ML) waters were characterized by high nitrate (~. 20. μM), low dissolved iron (DFe ~. 0.2. nM) and low silicate concentrations (below...
Dilution experiments were performed to quantify growth and mortality rates of
phytoplankton groups (as defined by pigment markers) for 5 wk in an iron-induced phytoplankton
bloom during the European Iron Fertilization Experiment (EIFEX) conducted in the Southern
Ocean. Rates could be reliably measured for the 2 main groups, diatoms and prymnesiophy...
Baleen and sperm whales, known collectively as the great whales, include the largest animals in the history of life on Earth. With high metabolic demands and large populations, whales probably had a strong influence on marine ecosystems before the advent of industrial whaling: as consumers of fish and invertebrates; as prey to other large-bodied pr...
Ocean iron fertilization experiments enable the quantitative study of processes shaping the structure and functioning of
pelagic ecosystems following perturbation under in situ conditions. EIFEX was conducted within a stationary eddy adjacent
to the Antarctic Polar Front over 38 days in February/March 2004 and induced a massive diatom bloom. Here,...
It has previously been asserted that baleen whales compete with fisheries by consuming potentially harvestable marine resources. The regularly applied “surplus-yield model” suggests that whale prey becomes available to fisheries if whales are removed, and has been presented as a justification for whaling. However, recent findings indicate that whal...
Understanding the biogeochemical processes regulating carbon cycling is central to mitigating atmospheric CO2 emissions. The role of living organisms has been accounted for, but the focus has traditionally been on contributions of plants and microbes. We develop the case that fully “animating” the carbon cycle requires broader consideration of the...
Sudden beaching of huge seaweed masses smother the coastline and form rotting piles on the shore. The number of reports of these events in previously unaffected areas has increased worldwide in recent years. These 'seaweed tides' can harm tourism-based economies, smother aquaculture operations or disrupt traditional artisanal fisheries. Coastal eut...
Significance
Silica-shelled diatoms dominate marine phytoplankton blooms and play a key role in ocean ecology and the global carbon cycle. We show how differences in ecological traits of dominant Southern Ocean diatom species, observed during the in situ European Iron Fertilization Experiment (EIFEX), can influence ocean carbon and silicon cycles....
[1] A closed eddy core in the Subantarctic Atlantic Ocean was fertilized twice with two tons of iron (as FeSO4), and the 300 km2 fertilized patch was studied for 39 days to test whether fertilization enhances downward particle flux into the deep ocean. Chlorophyll a and primary productivity doubled after fertilization, and photosynthetic quantum yi...
The oceans cover 70% of the planet's surface, and their planktonic inhabitants generate about half the global primary production, thereby playing a key role in modulating planetary climate via the carbon cycle. The ocean biota have been under scientific scrutiny for well over a century, and yet our understanding of the processes driving natural sel...
Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncerta...
The minerals involved in the formation of metazoan skeletons principally comprise glassy silica, calcium phosphate or carbonate. Because of their ancient heritage, glass sponges (Hexactinellida) may shed light on fundamental questions such as molecular evolution, the unique chemistry and formation of the first skeletal silica-based structures, and...
The iron-limited Southern Ocean plays an important role in regulating atmospheric CO(2) levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid fae...
Sleep is an enigma because we all know what it means and does to us, yet a scientific explanation for why animals including humans need to sleep is still lacking. However, the enigma can be resolved if the animal body is regarded as a purposeful machine whose moving parts are coordinated with spatial information provided by a disparate array of sen...
Dense aggregations of phytoplankton cells of one or more
species are loosely referred to as algal blooms. They play
a central role in the ecology and biogeochemistry of all
water bodies from ponds to the ocean, but a mechanistic
understanding of the factors leading to the rise and fall of
blooms is still lacking.
The most memorable LOHAFEX cruise came to an end on 17 March 2009 when RV Polarstern docked in the harbour of Punta Arenas (southern Chile) after successfully carrying out the longest iron fertilisation experiment so far (39 days). The two and a half month voyage, spent in the notorious Roaring Forties of the south - western Atlantic, was as close...
Of the various macro-engineering schemes proposed to mitigate global warming, ocean iron fertilization (OIF) is one that could be started at short notice on relevant scales. It is based on the reasoning that adding trace amounts of iron to iron-limited phytoplankton of the Southern Ocean will lead to blooms, mass sinking of organic matter and ultim...
It is premature to sell carbon offsets from ocean iron fertilization unless research provides the scientific foundation to evaluate risks and benefits.
Ocean iron fertilization (OIF), one of several ocean methods proposed for mitigating rising atmospheric CO2, involves stimulating net phytoplankton growth by releasing iron to certain parts of the surface ocean. The international oceanographic community has studied OIF, including 12 major field programs with small-scale, purposeful releases of iron...
This chapter provides a brief history of the conceptual framework of plankton evolutionary ecology to explain why the role of defense in the evolution of unicellular plankton has been neglected so far. The aim of this historical overview is also to point out what can be learned from studying the arms race: the other side of the coin. Given the rang...
IntroductionFootprints of the pastSteps to the futureConcluding comments
The responses of larger (>50 μm in diameter) protozooplankton groups to a phytoplankton bloom induced by in situ iron fertilization (EisenEx) in the Polar Frontal Zone (PFZ) of the Southern Ocean in austral spring are presented. During the 21 days of the experiment, samples were collected from seven discrete depths in the upper 150 m inside and out...
The dynamics, composition and grazing impact of microzooplankton were studied during the in situ iron fertilisation experiment EisenEx in the Antarctic Polar Frontal Zone in austral spring (November 2000). During the 21 day experiment, protozooplankton and small metazooplankton were sampled from the mixed layer inside and outside the patch using Ni...
The dynamics of phytoplankton species populations recorded during the 3-week, iron-fertilization experiment EisenEx carried out in spring in the Antarctic Polar Frontal Zone are presented and discussed as the difference between growth and mortality rates. Only two cosmopolitan diatom species, the centric Chaetoceros debilis and the pennate Pseudo-n...
Since the mid-1980s, our understanding of nutrient limitation of oceanic primary production has radically changed. Mesoscale iron addition experiments (FeAXs) have unequivocally shown that iron supply limits production in one-third of the world ocean, where surface macronutrient concentrations are perennially high. The findings of these 12 FeAXs al...
The dynamics of phytoplankton species populations recorded during the 3-week, iron-fertilization experiment EisenEx carried out in spring in the Antarctic Polar Frontal Zone are presented and discussed as the difference between growth and mortality rates. Only two cosmopolitan diatom species, the centric Chaetoceros debilis and the pennate Pseudo-n...
Size restoration by the auxospore that develops from the zygote is a crucial stage in diatom life cycles. However, information on sexual events in pelagic diatom species is very limited. We report for the first time auxospore formation by the pennate diatom Fragilariopsis kerguelensis (O'Hara) Hustedt during an iron-induced bloom in the Southern Oc...
1] The sources and sinks of atmospheric carbon dioxide over glacial/interglacial cycles are under debate. Variation in productivity of the Antarctic Circumpolar Current (ACC) could potentially play a significant role, but current interpretations of sedimentary geochemical proxies suggest that glacial productivity was not higher than today. We prese...
The responses of larger (>50 µm in diameter) protozooplankton groups to a phytoplankton bloom induced by in situ iron fertilization (EisenEx) in the Polar Frontal Zone (PFZ) of the Southern Ocean in austral spring are presented. During the 21 days of the experiment, samples were collected from seven discrete depths in the upper 150 m inside and out...
The dynamics, composition and grazing impact of microzooplankton were studied during the in situ iron fertilisation experiment EisenEx in the Antarctic Polar Frontal Zone in austral spring (November 2000). During the 21 day experiment, protozooplankton and small metazooplankton were sampled from the mixed layer inside and outside the patch using Ni...
Polar organisms have adapted their seasonal cycles to the dynamic interface between ice and water. This interface ranges from the micrometre-sized brine channels within sea ice to the planetary-scale advance and retreat of sea ice. Polar marine ecosystems are particularly sensitive to climate change because small temperature differences can have la...
From 3 to 6 November 2002, a colloquium was convened at the Benthos Laboratory of the Stazione Zoologica Anton Dohrn on Ischia, Italy, with the goal of evaluating the present status of the effects of diatoms on their main consumers, the planktonic copepods, and to develop future research strategies to enhance our understanding of such interactions....
From 3 to 6 November 2002, a colloquium was convened at the Benthos Laboratory of the Stazione Zoologica Anton Dohrn on Ischia, Italy, with the goal of evaluating the present status of the effects of diatoms on their main consumers, planktonic copepods, and to develop future research strategies to enhance our understanding of such interactions. The...
This review examines the links between pelagic ecology and ocean biogeochemistry with an
emphasis on the role of the Southern Ocean in global cycling of carbon and silica. The structure and
functioning of pelagic ecosystems is determined by the relationship between growth and mortality of its
species populations. Whereas the key role of iron supply...
Proprioception: is the sensory system that supports body posture and movement also the root of our understanding of physical laws?
The growth cycle in nutrient-rich, aquatic environments starts with a diatom bloom that ends in mass sinking of ungrazed cells and phytodetritus. The low grazing pressure on these blooms has been attributed to the inability of overwintering copepod populations to track them temporally. We tested an alternative explanation: that dominant diatom spec...
Ecophysiology Laboratory, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy. ianora@szn.it The growth cycle in nutrient-rich, aquatic environments starts with a diatom bloom that ends in mass sinking of ungrazed cells and phytodetritus. The low grazing pressure on these blooms has been attributed to the inability of overwintering cop...
Ample evidence has now accumulated showing that phytoplankton growth rates in the modern Southern Ocean are limited by iron availability. A major source of iron to the land-remote ocean is aeolian dust and it is very likely that higher dust input during glacials will have resulted in higher productivity and much greater CO2 drawdown. The phytoplank...
Diatoms are the major contributors to phytoplankton blooms in lakes and in the sea and hence are central in aquatic ecosystems and the global carbon cycle. All free-living diatoms differ from other phytoplankton groups in having silicified cell walls in the form of two 'shells' (the frustule) of manifold shape and intricate architecture whose funct...
Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and how science impacts upon all aspects of society and life.
This volume deals with institutions, implementation and innovations in the field of international marine environmental law. It discusses some controversial legal aspects of the marine environment in the context of UNCLOS, as a framework for national, regional and global action in the marine sector.
The purpose of this work is to faithfully report s...
The task of working group 4 was to examine the relationship between ecosystem functioning and biodiversity in marine systems. The definition of biodiversity used by the working group is the biological variability in ecosystems at the genetic, species and habitat level. The inventory of marine life is much closer to completion in Europe than in many...
The use of the North Sea is extremely multi-faceted and highly competitive. Within the vast variety of regulations inside the EU and in Germany, the regulative framework relevant to aquaculture is not yet complete. This chapter provides a short summary of the current legislative framework on international, national, and regional levels, which perta...
The frontal regions of the Antarctic Circumpolar Current (ACC) differ from other parts of the ACC due to higher phytoplankton concentrations and primary production rates. We hypothesise that the enhancement of primary production results from the mesoscale frontal dynamics, in particular the cross-front circulation related to baroclinic instability....
The quantitative distribution of dominant phytoplankton species was mapped at high spatial resolution (15km spacing) during a quasi-synoptic, mesoscale survey of hydrographical, chemical, pigment, and zooplankton fields carried out along the Antarctic Polar Front within a grid 140×130km2 during austral summer. A rapid assessment method for quantify...
Globally, humans impact environments and ecosystems faster than they become aware of their effects. The marine pelagic ecosystem includes a tremendously large and diverse environment, which might accordingly be considered to be resilient to externally forced changes, whether from humans or climate. This review considers that general hypothesis by p...
Ongoing changes in the morphology and ecology of the coastal zone and expected future scenarios with emphasis on the southern North Sea were discussed and research needs identified. The impact of sea level rise and the effects of resultant dyking activity need to be considered for the entire coastal zone as manipulation in one region can have unexp...
The discovery that certain phytoplankton species can render sea food highly toxic for humans was made only some 60 years ago. Information accumulating since then strongly suggests that harmful algae have had an impact on human diet, customs and also economy over many millennia. The current rapid advances in knowledge of algal toxins and their occur...
Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and how science impacts upon all aspects of society and life.
