Marc Kochzius

Vrije Universiteit Brussel | VUB · Department of Biology

Marine heatwaves trigger severe coral bleaching events that result in dramatic losses of coral reefs worldwide. An increasingly common method used to mitigate coral bleaching is to shade portions of reefs. However, as shaded corals become less exposed to environmental stress, shading has also been hypothesized to lower their thermal tolerance, whic...

Trace metals and metalloids are groups of chemical elements that naturally occur in low concentrations and cycle in the environment driven by natural processes and human activities. They have a persistent and bio-accumulative tendency in the environment, and certain trace metals and metalloids have become a public health concern. This study assesse...

This paper presents the observations of predation by the grouper Epinephelus quoyanus on sea turtle hatchlings in Chagar Hutang bay, Redang Island, Malaysia. Two of the eight collected specimens had hatchlings in their guts, whereas the remaining specimens had empty stomachs. This field report provides an in‐depth understanding of the E. quoyanus d...

Thermal stress can influence the recovery of fish released after capture. Vitality assessments using reflex and behavioural responses require that responses can be observed reliably, independent of temperature. Here, we tested whether reflex and behavioural impairment and survival of beam-trawled and discarded European plaice (Pleuronectes platessa...

Clownfish (subfamily Amphiprioninae) are an iconic group of coral reef fish that evolved a mutualistic interaction with sea anemones, which triggered the adaptive radiation of the clade. Within clownfishes, the “skunk complex” is particularly interesting. Besides ecological speciation, interspecific gene flow and hybrid speciation are thought to ha...

Thaisella chocolata is a marine gastropod (family Muricidae) occurring from northern Peru to central Chile. It is of economic importance in these countries, where hundreds of tons are caught every year. In combination with El Niño–Southern Oscillation events, fishing activity has led to the collapse of Chilean populations, raising concerns about th...

Anthropogenic activities such as mining pose a putative threat to deep-sea ecosystems and baseline studies of key indicator species are required to assess future loss of biodiversity. We examined population genetic structure, connectivity, cryptic diversity and phylogeography of the deep-sea scavenging amphipod, Abyssorchomene distinctus, using DNA...

Clownfish (subfamily Amphiprioninae) are an iconic group of coral reef fish that evolved a mutualistic interaction with sea anemones, which was shown to have triggered the adaptive radiation of the group. Within clownfishes, the skunk complex is particularly interesting as, besides ecological speciation, gene flow between species and hybrid speciat...

Western Indian Ocean countries have banned elasmobranch finning and enacted legislation to protect endangered elasmobranchs, however finned and morphologically deformed specimens are still landed and traded on Tanzanian fish markets. Such specimens are difficult to identify morphologically, and it is possible that protected elasmobranchs are among...

Increased human activity in the Antarctic Peninsula combined with accelerated melting of its glaciers highlights the importance of monitoring trace element concentrations. Surface sediment samples were collected around King George Island, Hope Bay and in the Bransfield Strait in February 2020 and were analysed by X-ray fluorescence spectroscopy and...

Various studies on population genetics in the Indo-Pacific that include the Coral Triangle region have revealed phylogeographic patterns in marine species populations. However, little is known about the population structure and connectivity pattern among the coral reefs in four seas surrounding Malaysia: the Strait of Malacca (Andaman Sea), the Sou...

Tanzania demarcated three prawn fishing zones along its coast to spread fishing pressure and help the prawn fishery to recover. However, it is unknown whether the demarcated zones correspond to the genetic stock structure of the world's most commercially important prawn, the giant tiger prawn (Penaeus monodon). Thus, this study used partial mitocho...

Context. Previous research has shown the presence of an endangered humpback whale population breeding off the Pacific coast of Central America. However, little is known about the density, size, social-group structure and spatial habitat use of this subpopulation. Aim. The study goal was to characterise a potential breeding subpopulation of humpback...

Populations of anemonefish species often show signs of local isolation due to limited dispersal potential and oceanographic conditions. Additionally, anthropogenic pressure, such as overharvesting and coral reef exploitation causes reduced population size, eventually leading to local extinction. The understanding of the genetic population structure...

There are currently 12 recognised extant species of giant clams (Cardiidae: Tridacninae) inhabiting the tropical waters of the Indo-Pacific. Six species have been newly described or rediscovered since 1982, such as the recently resurrected species Tridacna elongatissima in the Western Indian Ocean. In order to investigate the distribution range of...

To date, only one mitogenome from an Antarctic amphipod has been published. Here, novel complete mitochondrial genomes (mitogenomes) of two morphospecies are assembled, namely, Charcotia amundseni and Eusirus giganteus. For the latter species, we have assembled two mitogenomes from different genetic clades of this species. The lengths of Eusirus an...

Countries in the Western Indian Ocean (WIO) and along the Red Sea are particularly vulnerable to coral reef degradation, and understanding the degree of connectivity among coral reefs is a first step toward efficient conservation. The aim of this study is to investigate the genetic diversity, population structure and connectivity patterns of the br...

Ecological and social processes of the Spermonde Archipelago, South Sulawesi, Indonesia, have been intensively studied during the Science for the Protection of Indonesian Coastal Ecosystems (SPICE) program. The archipelago is of specific interest to better understand how intensive exploitation of marine resources results in the degradation of reef...

Coral reefs are important ecosystems in terms of their biodiversity and ecosystem functions. Particularly at local scales, coral reefs are vulnerable to natural and anthropogenic disturbances, leading to the degradation of reef health. Here, we employed two different methods to monitor reef health. First, we conducted line transect surveys to recor...

Background Genome-wide data are invaluable to characterize differentiation and adaptation of natural populations. Reduced representation sequencing (RRS) subsamples a genome repeatedly across many individuals. However, RRS requires careful optimization and fine-tuning to deliver high marker density while being cost-efficient. The number of genomic...

An integrative approach is crucial in discrimination of species, especially for taxa that are difficult to identify based on morphological characters. In this study, we combine genetics and morphology to assess the diversity of Pterasteridae, a sea star family diversified in deep-sea and polar environments. Because of their derived anatomy and the...

Genome-wide data are invaluable to characterize differentiation and adaptation of natural populations. Reduced representation sequencing (RRS) subsamples a genome repeatedly across many individuals. However, RRS requires careful optimization and fine-tuning to deliver high marker density while being cost-efficient. The number of genomic fragments c...

Populations of anemonefish species often show signs of local isolation due limited dispersal potential and oceanographic conditions. Additionally, anthropogenic pressure, such as overharvesting and coral reef exploitation causes reduced population size, eventually leading to local extinction. The understanding of the genetic population structure, a...

Estimates of population structure and gene flow allow exploring the historical and contemporary processes that determine a species’ biogeographic pattern. In mangroves, large-scale genetic studies to estimate gene flow have been conducted predominantly in the Indo-Pacific and Atlantic region. Here we examine the genetic diversity and connectivity o...

The Coral Triangle region contains the world’s highest marine biodiversity, however, these reefs are also the most threatened by global and local threats. A main limitation that prevents the implementation of adequate conservation measures is that connectivity and genetic structure of populations is poorly known. The aim of this study was to invest...

Coral reefs provide essential goods and services but are degrading at an alarming rate due to local and global anthropogenic stressors. The main limitation that prevents the implementation of adequate conservation measures is that connectivity and genetic structure of populations are poorly known. Here, the genetic diversity and connectivity of the...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The Northern Mozambique Channel is a treasure of unique oceanography, rich coral reefs, migrating tuna, and whales, bounded by the Comoros, France, Madagascar, Mozambique, Seychelles, and Tanzania. Its living resources are relatively intact and of great importance for food and livelihood security and the developing economies of its surrounding coun...

Pulau Redang and Pulau Tioman have experienced huge tourism growth over the last two decades, but minimal sewage treatment may threaten the resilience of their coral reefs. This study uses stable isotope techniques to identify suitable bioindicators of sewage nutrients (δ 15 N) at these islands by measuring macroalgae (Lobophora spp.), gastropods (...

The market demand for octopus grows each year, but landings are decreasing, and prices are rising. The present study investigated (1) diversity of Octopodidae in the Western Indian Ocean (WIO) and (2) connectivity and genetic structure of Octopus cyanea and O. vulgaris populations in order to obtain baseline data for management plans. A fragment of...

The impact of salt farming on the habitats and food sources of Austruca occidentalis and Littoraria subvittata was studied in mangroves along the coast of Tanzania using stable isotopes (¹³C and ¹⁵N) and sediment particle size analysis. The ¹³C and ¹⁵N stable isotope composition in mangrove leaves, sediments and invertebrate tissues, were used to e...

The protection of marine biodiversity is considered a global priority, as exemplified in the Convention on Biological Diversity's Aichi targets and in Sustainable Development Goal 14. Marine protected areas (MPAs) are considered to be effective conservation and fisheries management tools that generate various ecological and social-economic benefits...

Aim To test hypothesized biogeographic partitions of the tropical Indo‐Pacific Ocean with phylogeographic data from 56 taxa, and to evaluate the strength and nature of barriers emerging from this test. Location The Indo‐Pacific Ocean. Time period Pliocene through the Holocene. Major taxa studied Fifty‐six marine species. Methods We tested eight...

This study investigates the genetic population structure and connectivity of Acanthurus triostegus in five Indo‐Pacific biogeographic regions (western and eastern Indian Ocean, western, central and eastern Pacific Ocean), using a mitochondrial DNA marker spanning the ATPase8 and ATPase6 gene regions. In order to assess the phylogeography and geneti...

Populations of the clown anemonefish in Spermonde Archipelago, one of the main collection sites for ornamental fish in Indonesia, are potentially overfished, which might lead to a reduction in population size and genetic diversity. Loss of genetic diversity can reduce the adaptability, population persistence and productivity of the targeted species...

In this contribution, we determine the genetic population structure in the Skunk Clownfish (Amphiprion akallopsisos) across the Indian Ocean, and on a smaller geographic scale in the Western Indian Ocean (WIO). Highly restricted gene flow was discovered between populations on either side of the Indian Ocean using the control region as a mitochondri...

95% Confidence Intervals ϕst and Fst-values. (DOCX)

Overview of microsatellite markers tested for A. akallopisos. (DOCX)

(A) Pairwise ϕst-values among populations using reduced datasets. (B) Pairwise Fst-values among populations using reduced datasets. (C) Composition of reduced populations with eight randomly chosen individuals. (D) ϕct–values of hierarchical AMOVAs. (E) Fct–values of hierarchical AMOVAs. (DOCX)

DAPC of WIO individuals defining 2 clusters. (DOCX)

PCA of the WIO using 3 predefined groups. (DOCX)

Structure k = 3 for WIO. (DOCX)

Aim The aim of this study was to test historical and contemporary influences on population structure in the giant clams, Tridacna maxima (Röding, 1798) and T. crocea (Lamarck, 1819). To refine the location of clade boundaries within a newly resurrected species, Tridacna noae (Röding, 1798). Location Indo‐Australian archipelago, including Indonesia...

To investigate gene-flow patterns in the western Indian Ocean (WIO), tissue samples of Terebralia palustris were collected along the coasts of East Africa and Madagascar. A fragment of the mitochondrial cyto-chrome c oxidase subunit I (COI) gene was sequenced in 308 individuals from 18 sites. Based on a COI fragment of 624 base pairs, 43 haplotypes...

Naturforscher versuchen seit Jahrhunderten, die biologische Vielfalt der Erde zu beschreiben und zu klassifizieren. In jüngerer Zeit werden dazu immer häufiger DNA-Sequenzen genutzt, die durch die rasante Entwicklung in der Molekulargenetik und Bioinformatik in großen Mengen erarbeitet und zur Stammbaumanalyse genutzt werden können. Die Zeitmaschin...

The giant mud crab Scylla serrata provides an important source of income and food to coastal communities in East Africa. However, increasing demand and exploitation due to the growing coastal population, export trade, and tourism industry are threatening the sustainability of the wild stock of this species. Because effective management requires a c...

Variable sites among the East African Scylla serrata COI haplotypes. (DOCX)

Genetic population structure & connectivity of mangrove whelk

The coastal population in East Africa is growing rapidly but sewage treatment and recycling facilities in major cities and towns are poorly developed. Since estuarine mangroves are the main hotspots for pollutants, there is a potential for contaminants to accumulate in edible fauna and threaten public health. This study analysed trace metals in mus...

Small island archipelagos with fringing and dispersed reef systems represent special marine ecosystems, providing a patchy habitat for many coral reef organisms. Although geographic distances may be short, it is still unclear if such environments are inhabited evenly with panmictic conditions or if limited connectivity between marine populations, e...

The fiddler crab Austruca occidentalis is a dominant species in mangrove forests along the East African coast. It enhances soil aeration and, through its engineering activities, makes otherwise-inaccessible food available for other marine organisms. Despite its importance, the habitat of A. occidentalis is threatened by human activities. Clearing t...

Scoring reflex responsiveness and injury of aquatic organisms has gained popularity as predictors of discard survival. Given this method relies upon the individual interpretation of scoring criteria, an evaluation of its robustness is done here to test whether protocol-instructed, multiple raters with diverse backgrounds (research scientist, techni...

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of injury types (the intermediate category ‘1’ was assigned to absent and ‘2’ to present). (DOCX)

Wald III Chi-square test results of a linear mixed model (LMM) fitted to continuous reflex scores. (DOCX)

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of categorical reflex scores (‘weak’ included in the strong category). (DOCX)

Wald III Chi-square test results of a linear mixed model (LMM) fitted to reflex & injury indices (based on categorical scores with a value of 0.33 assigned to injury category ‘1’ and 0.66 assigned to a weak reflex and injury category ‘2’). (DOCX)

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of categorical reflex scores (‘weak’ included in the absent category.) (DOCX)

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of continuous reflex scores. (DOCX)

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of injury types (the intermediate categories ‘1’ and ‘2’ were assigned to present). (DOCX)

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of reflex indices (based on categorical scores with a value of 0.66 assigned to a weak reflex reponse). (DOCX)

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of reflex & injury indices (based on categorical scores). (DOCX)

Post-hoc Tukey test results of pairwise comparisons between raters (A, B, and C) of least-square means (Lsmean ± SE) and lower and upper 95% confidence intervals (CI) of continuous individual reflex indices. (DOCX)

Cox proportional hazard (coxph) regression model for a mean rater with fish status (dead or alive) as response variable and the reflex index (based on categorical or continuous scores—R.cat or R.con, respectively) or reflex and injury (R&I) index and its interaction with fish size (TL) as independent variables. (DOCX)

Wald III Chi-square test results of a linear mixed model (LMM) fitted to reflex indices (based on categorical scores with a value of 0.66 assigned to weak). (DOCX)

Wald III Chi-square test results of a linear mixed model (LMM) fitted to continuous reflex indices. (DOCX)

In tropical coastal ecosystems mangrove forests are important as feeding, spawning, breeding and nursery grounds for many marine species. High human population pressure in coastal areas has led to the loss and deterioration of mangrove habitats. Solar salt production can affect these habitats along the East African coast. Littorinid snails live on...

The skunk clownfish (Amphiprion akallopisos) has a disjunct distribution, occurring in the Eastern Indian Ocean (EIO) and the Western Indian Ocean (WIO), separated by several thousands of kilometres. Information on connectivity of marine species is very important for the correct spacing of marine protected areas, a powerful instrument for the prote...

The coral reef sea star Linckia laevigata is common on shallow water coral reefs of the Indo-West Pacific. Its large geographic distribution and comprehensive data from previous studies makes it suitable to examine genetic differentiation and connectivity over large geographical scales. Based on partial sequences of the mitochondrial cytochrome oxi...

Hierarchical AMOVA based on mitochondrial control region sequences from Linckia laevigata with alternative groupings of sample sites from the WIO. (DOCX)

AMOVA results on dataset that excludes all sample sites with less than 10 individuals. (DOCX)

Pairwise ΦST-values among populations of Linckia laevigata in the Western Indian Ocean (for abbreviations see Table 1). (DOCX)

Mid-trophic pelagic fish are essential components of marine ecosystems because they represent the link between plankton and higher predators. Moreover, they are the basis of the most important fisheries resources; for example, in African waters. In this study, we have sampled pelagic fish larvae in the Eastern Atlantic Ocean along a latitudinal gra...