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Bray JP, Hewitt CLR, Hulme PE. Bridging aquatic invasive species threats across multiple sectors through One Biosecurity. Bioscience 2024; 74:440-449. [PMID: 39156613 PMCID: PMC11328144 DOI: 10.1093/biosci/biae049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 04/15/2024] [Accepted: 05/05/2024] [Indexed: 08/20/2024] Open
Abstract
Understanding the magnitude of biosecurity risks in aquatic environments is increasingly complex and urgent because increasing volumes of international shipping, rising demand for aquaculture products, and growth in the global aquarium trade, are accelerating invasive alien species spread worldwide. These threats are especially pressing amid climate and biodiversity crises. However, global and national biosecurity systems are poorly prepared to respond because of fragmented research and policy environments, that often fail to account for risks across sectors or across stakeholder needs and fail to recognize similarities in the processes underpinning biological invasions. In the present article, we illustrate the complex network of links between biosecurity threats across human, animal, plant, and environment sectors and propose a universal approach to risk assessment. One Biosecurity is a holistic, interdisciplinary approach that minimizes biosecurity risks across human, animal, plant, algal, and ecosystem health and is critical to reduce redundancy and increase cross-sectoral cohesion to improve policy, management, and research in aquatic biosecurity.
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Affiliation(s)
- Jonathan Peter Bray
- The Centre for One Biosecurity Research, Analysis and Synthesis
- Department of Pest-Management and Conservation at Lincoln University, Christchurch, Canterbury, New Zealand
| | | | - Philip Eric Hulme
- The Centre for One Biosecurity Research, Analysis and Synthesis
- Department of Pest-Management and Conservation at Lincoln University, Christchurch, Canterbury, New Zealand
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Role of Macrofaunal Communities in the Vistula River Plume, the Baltic Sea-Bioturbation and Bioirrigation Potential. BIOLOGY 2023; 12:biology12020147. [PMID: 36829426 PMCID: PMC9952380 DOI: 10.3390/biology12020147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/09/2023] [Accepted: 01/14/2023] [Indexed: 01/20/2023]
Abstract
Macrozoobenthos plays a key role in the transformation of inputs from rivers to the sea, such as nutrients, organic matter, or pollutants, and influences biogeochemical processes in the sediments through bioturbation and bioirrigation activity. The purpose of our study was to determine the structure of benthic communities, their bioturbation (BPC) and bioirrigation potential (IPC), and the vertical distribution of macrofauna in the Gulf of Gdańsk. The study revealed changes in the structure of benthic communities and, consequently, in the bioturbation and bioirrigation potential in the study area. Despite the presence of diverse and rich communities in the coastal zone, BPC and IPC values, although high, were formed by a few species. Both indices were formed mainly by the clam Macoma balthica and polychaetes, although the proportion of polychaetes in IPC was higher than in BPC. In the deepest zones, the communities became poorer until they eventually disappeared, along with all macrofaunal functions. Both indices changed similarly with distance from the Vistula River mouth, and there was a very strong correlation between them. We also demonstrated that the highest diversity of the macrofauna was observed in the upper first cm of the sediment, but the highest biomass was observed in deeper layers-at a depth of up to 6 cm, and single individuals occurred even below 10 cm.
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Lam-Gordillo O, Huang J, Barceló A, Kent J, Mosley LM, Welsh DT, Simpson SL, Dittmann S. Restoration of benthic macrofauna promotes biogeochemical remediation of hostile sediments; An in situ transplantation experiment in a eutrophic estuarine-hypersaline lagoon system. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 833:155201. [PMID: 35421488 DOI: 10.1016/j.scitotenv.2022.155201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/25/2022] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
Estuarine ecosystems have very high ecological and economic value, and also act as a buffer for coastal oceans by processing nutrient inputs from terrestrial sources. However, ongoing pressures from increased urbanisation and agriculture, overlaid by climate change, has reduced inflows and increased nutrient loads that challenge the health and buffering capacity of these ecosystems. This study aimed to investigate whether restoring the bioturbating activity of Simplisetia aequisetis (Polychaeta: Nereididae) and other macrofauna could improve biogeochemical conditions in 'hostile' (i.e. hypersaline, sulfide-rich) sediments. To achieve this aim, we conducted an in situ experiment in the Coorong estuarine-lagoon ecosystem, translocating hostile hypersaline sediments, devoid of bioturbating macrofauna, to a 'healthy' (lower salinity) location where macrobenthic fauna naturally occur, and manipulating the S. aequisetis density in the sediments. Porewater, solid-phase, and diffusive equilibrium and diffusive gradient in thin-films (DET/DGT) measurements showed that bioturbation by macrobenthic fauna significantly influenced sediment biogeochemistry and remediated hostile conditions in sediment within a short time (four weeks) irrespective of S. aequisetis density. Bioturbation promoted sediment oxygenation, while salinity and the concentrations of total organic carbon and porewater sulfide, ammonium, and phosphate all decreased over time at all sediment depths. This research highlights the importance of macrobenthic communities and their functional traits for improving sediment conditions, promoting resilience to eutrophication, providing a nature-based remediation option, and in general ensuring healthy functioning of estuarine ecosystems.
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Affiliation(s)
- Orlando Lam-Gordillo
- College of Science and Engineering, Flinders University, GPO Box 2100, Kaurna Country, Adelaide, SA 5001, Australia.
| | - Jianyin Huang
- University of South Australia, STEM, Scarce Resources and Circular Economy (ScaRCE), Kaurna Country, SA 5095, Australia
| | - Andrea Barceló
- College of Science and Engineering, Flinders University, GPO Box 2100, Kaurna Country, Adelaide, SA 5001, Australia
| | - Jordan Kent
- College of Science and Engineering, Flinders University, GPO Box 2100, Kaurna Country, Adelaide, SA 5001, Australia
| | - Luke M Mosley
- School of Biological Sciences, University of Adelaide, Kaurna Country, Adelaide, Australia
| | - David T Welsh
- University of South Australia, STEM, Scarce Resources and Circular Economy (ScaRCE), Kaurna Country, SA 5095, Australia; School of Environment, Griffith University, Yugambeh/Kombumerri Country, Queensland, Australia
| | - Stuart L Simpson
- Centre for Environmental Contaminants Research, CSIRO Land & Water, Tharawal Country, Lucas Heights, NSW 2234, Australia
| | - Sabine Dittmann
- College of Science and Engineering, Flinders University, GPO Box 2100, Kaurna Country, Adelaide, SA 5001, Australia
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Lam-Gordillo O, Mosley LM, Simpson SL, Welsh DT, Dittmann S. Loss of benthic macrofauna functional traits correlates with changes in sediment biogeochemistry along an extreme salinity gradient in the Coorong lagoon, Australia. MARINE POLLUTION BULLETIN 2022; 174:113202. [PMID: 34864464 DOI: 10.1016/j.marpolbul.2021.113202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/15/2021] [Accepted: 11/24/2021] [Indexed: 06/13/2023]
Abstract
Estuarine ecosystems are considered hotspots for productivity, biogeochemical cycling and biodiversity, however, their functions and services are threatened by several anthropogenic pressures. We investigated how abundance and diversity of benthic macrofauna, and their functional traits, correlate to sediment biogeochemistry and nutrient concentrations throughout an estuarine-to-hypersaline lagoon. Benthic communities and functional traits were significantly different across the sites analysed, with higher abundance and more traits expressed in the estuarine region. The results revealed that the benthic trait differences correlated with sediment biogeochemistry and nutrient concentrations in the system. The estuarine regions were dominated by high abundance of large burrowing and bioturbating macrofauna, promoting nutrient cycling and organic matter mineralisation, while these organisms were absent in the hypersaline lagoon, favouring accumulation of organic matter and nutrients in the sediment. The results highlight the importance of preserving healthy benthic communities to maintain ecosystem functioning and mitigate the potential impacts of eutrophication in estuarine ecosystems.
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Affiliation(s)
- Orlando Lam-Gordillo
- College of Science and Engineering, Flinders University, GPO Box 2100, Kaurna Country, Adelaide, SA 5001, Australia.
| | - Luke M Mosley
- School of Biological Sciences, University of Adelaide, Kaurna Country, Adelaide, Australia
| | - Stuart L Simpson
- Centre for Environmental Contaminants Research, CSIRO Land & Water, Tharawal Country, Lucas Heights, NSW 2234, Australia
| | - David T Welsh
- School of Environment, Griffith University, Yugambeh/Kombumerri Country, Queensland, Australia
| | - Sabine Dittmann
- College of Science and Engineering, Flinders University, GPO Box 2100, Kaurna Country, Adelaide, SA 5001, Australia
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Ek C, Faxneld S, Nyberg E, Rolff C, Karlson AML. The importance of adjusting contaminant concentrations using environmental data: A retrospective study of 25 years data in Baltic blue mussels. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 762:143913. [PMID: 33373754 DOI: 10.1016/j.scitotenv.2020.143913] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/15/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
To improve the statistical power of detecting changes in contaminant concentrations over time, it is critical to reduce both the within- and between-year variability by adjusting the data for relevant confounding variables. In this study, we present a method for handling multiple confounding variables in contaminant monitoring. We evaluate the highly variable temporal trends of Polycyclic Aromatic Hydrocarbons (PAHs) in blue mussels from the central Baltic Sea during the period 1987-2016 (data from 25 years during this period) using various regression analyses. As potential explanatory variables related to PAH exposure, we use mussel size and retrospective analyses of mussel δ15N and δ13C (representing large scale biogeochemical changes as a result of e.g. eutrophication and terrestrial inputs). Environmental data from concurrent monitoring programmes (seasonal data on Chlorophyll-a, salinity and temperature in the water column, bioturbation of sediment dwelling fauna) were included as variables related to feeding conditions. The concentrations of high-molecular-weight and low-molecular-weight PAHs in blue mussel were statistically linked to different combinations of environmental variables. Adjustment using these predictors decreased the coefficient of variation in all 15 PAHs tested and improved the statistical power to detect changes. Moreover, the adjustment also resulted in a significant downward trend for fluoranthene that could not be detected initially. For another PAH, benzo(g,h,i)perylene, adjustment which reduced variation resulted in the loss of an apparent downward trend over time. Hence, our study highlights the importance of using auxilliary data to reduce variability caused by environmental factors with general effects on physiology when assessing contaminant time trends. Furthermore, it illustrates the importance of extensive and well designed monitoring programmes to provide relevant data.
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Affiliation(s)
- Caroline Ek
- Department of Ecology, Environment and Plant Science, SE-106 91, Stockholm University, Stockholm, Sweden
| | - Suzanne Faxneld
- Department of Environmental Research and Monitoring, Swedish Museum of Natural History, P.O. 50007, SE-104 05 Stockholm, Sweden
| | - Elisabeth Nyberg
- Swedish Environmental Protection Agency, Naturvårdsverket, SE-106 48 Stockholm, Stockholm, Sweden
| | - Carl Rolff
- Stockholm University Baltic Sea Centre, SE 106-91 Stockholm, Sweden
| | - Agnes M L Karlson
- Department of Ecology, Environment and Plant Science, SE-106 91, Stockholm University, Stockholm, Sweden; Stockholm University Baltic Sea Centre, SE 106-91 Stockholm, Sweden.
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Mdaini Z, Telahigue K, Hajji T, Rabeh I, El Cafsi M, Tremblay R, Gagné JP. Comparative biomarker responses to urban pollution in three polychaete species: Perinereis cultrifera, Diopatra neapolitana, and Marphysa sanguinea from the lagoon of Tunis. ENVIRONMENTAL MONITORING AND ASSESSMENT 2021; 193:119. [PMID: 33569704 DOI: 10.1007/s10661-021-08906-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
Coastal lagoons are among the most vulnerable ecosystems as they are often exposed to different anthropogenic activities. The Polychaetes, which are dominant components in macrobenthic community, are particularly exposed to contamination. The current study was designed to assess and compare the sensitivity of different polychaetes species towards urban pollution. To do this, three polychaete species: Perinereis cultrifera, Diopatra neapolitana, and Marphysa sanguinea, were collected from the Tunis South Lagoon during summer 2013. A set of biomarkers indicative of genotoxicity (DNA damage), biotransformation, and oxidative stress (glutathione S-transferase, GST) as well as immune response (cyclooxygenase activity (COX), lysozyme activity, and nitric oxide level (NOx)), was used. The results revealed that D. neapolitana and P. cultrifera exhibited higher genetic alteration and GST activity and more prominent immune response when compared with M. sanguinea. These findings denote of the higher sensitivity of D. neapolitana and P. cultrifera to urban pollution and suggest their possible use in environmental biomonitoring programs.
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Affiliation(s)
- Zied Mdaini
- Laboratoire D'Ecologie, Biologie Et Physiologie Des Organismes Aquatiques LR18ES41, Faculté Des Sciences de Tunis, Université Tunis El Manar, 2092, Tunis, Tunisia
- Institut Des Sciences de La Mer de Rimouski, Université du Québec À Rimouski, 310 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
| | - Khaoula Telahigue
- Laboratoire D'Ecologie, Biologie Et Physiologie Des Organismes Aquatiques LR18ES41, Faculté Des Sciences de Tunis, Université Tunis El Manar, 2092, Tunis, Tunisia.
| | - Tarek Hajji
- Laboratoire de Biotechnologie Et Valorisation Des Bio-Géo Ressources LR11ES31, Institut Supérieur de Biotechnologie de Sidi Thabet, Université La Manouba, Biotechpole Sidi Thabet, 2020, Ariana, Tunisia
| | - Imen Rabeh
- Laboratoire D'Ecologie, Biologie Et Physiologie Des Organismes Aquatiques LR18ES41, Faculté Des Sciences de Tunis, Université Tunis El Manar, 2092, Tunis, Tunisia
| | - M'hamed El Cafsi
- Laboratoire D'Ecologie, Biologie Et Physiologie Des Organismes Aquatiques LR18ES41, Faculté Des Sciences de Tunis, Université Tunis El Manar, 2092, Tunis, Tunisia
| | - Rejean Tremblay
- Institut Des Sciences de La Mer de Rimouski, Université du Québec À Rimouski, 310 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
| | - Jean Pierre Gagné
- Institut Des Sciences de La Mer de Rimouski, Université du Québec À Rimouski, 310 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
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Contrasting Effects of Bioturbation Studied in Intact and Reconstructed Estuarine Sediments. WATER 2020. [DOI: 10.3390/w12113125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Macrofauna can produce contrasting biogeochemical effects in intact and reconstructed sediments. We measured benthic fluxes of oxygen, inorganic carbon, and nitrogen and denitrification rates in intact sediments dominated by a filter and a deposit feeder and in reconstructed sediments added with increasing densities of the same organisms. Measurements in reconstructed sediments were carried out 5 days after macrofauna addition. The degree of stimulation of the measured fluxes in the intact and reconstructed sediments was then compared. Results confirmed that high densities of bioturbating macrofauna produce profound effects on sediment biogeochemistry, enhancing benthic respiration and ammonium recycling by up to a factor of ~3 and ~9, respectively, as compared to control sediments. The deposit feeder also increased total denitrification by a factor of ~2, whereas the filter feeder activity did not stimulate nitrogen removal. Moreover, the effects of deposit feeders on benthic fluxes were significantly higher (e.g., on respiration and ammonium recycling) or different (e.g., on denitrification) when measured in intact and reconstructed sediments. In intact sediments, deposit feeders enhanced the denitrification coupled to nitrification and had no effects on the denitrification of water column nitrate, whereas in reconstructed sediments, the opposite was true. This may reflect active burrowing in reconstructed sediments and the long time needed for slow growing nitrifiers to develop within burrows. Results suggest that, in bioturbation studies, oversimplified experimental approaches and insufficient preincubation time might lead to wrong interpretation of the role of macrofauna in sediment biogeochemistry, far from that occurring in nature.
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Carstensen J, Conley DJ, Almroth-Rosell E, Asmala E, Bonsdorff E, Fleming-Lehtinen V, Gustafsson BG, Gustafsson C, Heiskanen AS, Janas U, Norkko A, Slomp C, Villnäs A, Voss M, Zilius M. Factors regulating the coastal nutrient filter in the Baltic Sea. AMBIO 2020; 49:1194-1210. [PMID: 31707582 PMCID: PMC7128010 DOI: 10.1007/s13280-019-01282-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 09/17/2019] [Accepted: 09/23/2019] [Indexed: 05/30/2023]
Abstract
The coastal zone of the Baltic Sea is diverse with strong regional differences in the physico-chemical setting. This diversity is also reflected in the importance of different biogeochemical processes altering nutrient and organic matter fluxes on the passage from land to sea. This review investigates the most important processes for removal of nutrients and organic matter, and the factors that regulate the efficiency of the coastal filter. Nitrogen removal through denitrification is high in lagoons receiving large inputs of nitrate and organic matter. Phosphorus burial is high in archipelagos with substantial sedimentation, but the stability of different burial forms varies across the Baltic Sea. Organic matter processes are tightly linked to the nitrogen and phosphorus cycles. Moreover, these processes are strongly modulated depending on composition of vegetation and fauna. Managing coastal ecosystems to improve the effectiveness of the coastal filter can reduce eutrophication in the open Baltic Sea.
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Affiliation(s)
- Jacob Carstensen
- Department of Bioscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - Daniel J. Conley
- Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Sweden
| | | | - Eero Asmala
- Tvärminne Zoological Station, University of Helsinki, J.A. Palmenin tie 260, 10900 Hanko, Finland
| | - Erik Bonsdorff
- Environmental and Marine Biology, Åbo Akademi University, BioCity, 20500 Turku, Finland
| | | | - Bo G. Gustafsson
- Tvärminne Zoological Station, University of Helsinki, J.A. Palmenin tie 260, 10900 Hanko, Finland
- Stockholm University Baltic Sea Centre, 106 91 Stockholm, Sweden
| | - Camilla Gustafsson
- Tvärminne Zoological Station, University of Helsinki, J.A. Palmenin tie 260, 10900 Hanko, Finland
| | | | - Urzsula Janas
- Department of Experimental Ecology of Marine Organisms, Institute of Oceanography, University of Gdańsk, al. Marsz. J. Pilsudskiego 46, 81-378 Gdynia, Poland
| | - Alf Norkko
- Tvärminne Zoological Station, University of Helsinki, J.A. Palmenin tie 260, 10900 Hanko, Finland
| | - Caroline Slomp
- Department of Earth Sciences, Utrecht University, Princetonlaan 8A, 3584 CB Utrecht, The Netherlands
| | - Anna Villnäs
- Tvärminne Zoological Station, University of Helsinki, J.A. Palmenin tie 260, 10900 Hanko, Finland
| | - Maren Voss
- Department of Biological Oceanography, Leibniz Institute of Baltic Sea Research, Seestr. 15, 18119 Rostock, Germany
| | - Mindaugas Zilius
- Marine Research Institute, Universiteto al. 17, 92294 Klaipeda, Lithuania
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Effects of the Bioturbating Marine Yabby Trypaea australiensis on Sediment Properties in Sandy Sediments Receiving Mangrove Leaf Litter. JOURNAL OF MARINE SCIENCE AND ENGINEERING 2019. [DOI: 10.3390/jmse7120426] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Laboratory mesocosm incubations were undertaken to investigate the influence of burrowing shrimp Trypaea australiensis (marine yabby) on sediment reworking, physical and chemical sediment characteristics and nutrients in sandy sediments receiving mangrove (Avicennia marina) leaf litter. Mesocosms of sieved, natural T. australiensis inhabited sands, were continually flushed with fresh seawater and pre-incubated for 17 days prior to triplicates being assigned to one of four treatments; sandy sediment (S), sediment + yabbies (S+Y), sediment + leaf litter (organic matter; S+OM) and sediment + yabbies + leaf litter (S+Y+OM) and maintained for 55 days. Mangrove leaf litter was added daily to treatments S+OM and S+Y+OM. Luminophores were added to mesocosms to quantify sediment reworking. Sediment samples were collected after the pre-incubation period from a set of triplicate mesocosms to establish initial conditions prior to the imposition of the treatments and from the treatment mesocosms at the conclusion of the 55-day incubation period. Yabbies demonstrated a clear effect on sediment topography and leaf litter burial through burrow creation and maintenance, creating mounds on the sediment surface ranging in diameter from 3.4 to 12 cm. Within S+Y+OM sediments leaf litter was consistently removed from the surface to sub-surface layers with only 7.5% ± 3.6% of the total mass of leaf detritus added to the mesocosms remaining at the surface at the end of the 55-day incubation period. Yabbies significantly decreased sediment wet-bulk density and increased porosity. Additionally, T. australiensis significantly reduced sediment bio-available ammonium (NH4+bio) concentrations and altered the shape of the concentration depth profile in comparison to the non-bioturbated mesocosms, indicating influences on nutrient cycling and sediment-water fluxes. No significant changes for mean apparent biodiffusion coefficients (Db) and mean biotransport coefficients (r), were found between the bioturbated S+Y and S+Y+OM mesocosms. The findings of this study provide further evidence that T. australiensis is a key-species in shallow intertidal systems playing an important role as an ‘ecosystem engineer’ in soft-bottom habitats by significantly altering physical and chemical structures and biogeochemical function.
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Abstract
Coastal lagoons display a wide range of physico-chemical conditions that shape benthic macrofauna communities. In turn, benthic macrofauna affects a wide array of biogeochemical processes as a consequence of feeding, bioirrigation, ventilation, and excretion activities. In this work, we have measured benthic respiration and solute fluxes in intact sediment cores with natural macrofauna communities collected from four distinct areas within the Sacca di Goro Lagoon (NE Adriatic Sea). The macrofauna community was characterized at the end of the incubations. Redundancy analysis (RDA) was used to quantify and test the interactions between the dominant macrofauna species and solute fluxes. Moreover, the relevance of macrofauna as driver of benthic nitrogen (N) redundancy analysis revealed that up to 66% of the benthic fluxes and metabolism variance was explained by macrofauna microbial-mediated N processes. Nitrification was stimulated by the presence of shallow (corophiids) in combination with deep burrowers (spionids, oligochaetes) or ammonium-excreting clams. Deep burrowers and clams increase ammonium availability in burrows actively ventilated by corophiids, which creates optimal conditions to nitrifiers. However, the stimulatory effect of burrowing macrofauna on nitrification does not necessarily result in higher denitrification as processes are spatially separated.
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