Niall Broekhuizen


Job title and place of work

Ecological Modeller, NIWA, Hamilton.

What is your role in the CARIM project? What work package are you contributing to?

RA2 - I am a member of a team who are using the ROMS (Regional Ocean Modelling System) to derive a quantitative understanding of how the pH of the Firth of Thames and Hauraki Gulf has been influenced by changing land-use patterns over the past millennium.

I am also looking at how ongoing climate change will further influence the pH of the system. 

What do you do on an average work day?

My job title is Ecological Modeller. The terms ‘model’ and ‘modeller’ may mean different things to different folks.  In the context of my job description, I consider that a model is the combination of: (a) a formal mathematical description of how key components of some system interact and (b) a computer-code representation of those equations and the methods required to produce solutions to the equations.

An ecological modeller specialises in developing descriptions of how living things interact with their environment. For much of my career, I have focussed upon models of plankton dynamics in the coastal marine environment (especially in relation to shellfish farming and finfish farming). I have also developed models of numerous other types of system (forest insect pests, seabird foraging, organic matter degradation in wastewater treatment plants, invertebrate dynamics in streams). 

Models come in many forms: qualitative verbal descriptions, statistical descriptions derived from examining historical data, dynamical-quasi-mechanistic models
All models are simplified, abstractions of reality.  They focus upon features that are believed to be most relevant to the problem at hand. 

The process of developing a new model involves careful discussion with relevant experts and other interested parties in order to fully understand what questions are going to be put to the model. These questions determine what features the model must be able to yield. In turn, that guides the structure of the model (what building clocks and relationships it will explicitly represent). Having determined an appropriate structure, the modeller then writes a formal mathematical description.

Subsequently, that will be converted to computer-code and embedded within the algorithms that will solve it.  In conjunction with colleagues, the modeller will search for data that will (a) provide inputs to the model, (b) provide means of validating the model (demonstrating that it is (or is not) performing well. Often, suitable data will not be available. In those situations, the modeller may work within a team to design observational- or experimental studies that will yield the requisite data.

The simplest models can be built in a matter of hours, but more complex ones may take months to construct.  Often, the models (and associated experiment/observational programmes) are iteratively refined and/or extended over several years.

Why is studying coastal acidification important?

World-wide, the coastal marine zone accounts for a considerable amount of annual marine primary production.  Marine aquaculture is restricted to the coastal area. At present, in New Zealand it has an annual value of $350 million and aspires to reach $1 billion by 2025. Commercial fisheries catches already have a value of approximately $1 billion (albeit that many of those fish are taken from waters beyond the immediate coastal zone).  

The coastal zone is also a mainstay of New Zealand’s recreation industries and our national identity.  It has been estimated that around 20% of New Zealand’s population participate in recreational fishing.  

The coastal zone carries values beyond those associated with fishing and aquaculture.  Many of those who visit coastal baches or camp-grounds will never throw a hook into the water.  Instead, they find attraction in viewing and/or swimming in clear waters overlying diverse, healthy benthic habitats and supporting lively communities of large fish, marine mammals, seabirds etc.

Whilst it is not clear that coastal acidification will dramatically influence the structure and function of New Zealand’s coastal marine foodweb, there is some evidence to suggest that at least subtle changes may occur. The cultural and financial losses that might arise justify research aimed at quantifying the changes that will arise – as a means of informing debate around mitigation and adaptation

What study did you do at high school? And after high school?

I studied mathematics, physical sciences and biology at secondary school.  My undergraduate degree was in biology (specializing in population modelling). Thereafter, I completed a PhD (studying the population dynamics of a forest insect pest).

After completing my PhD, I took a four year psot-doctoral position where I worked as part of a team building an ecosystem model of the North Sea. My responsibilities were for the zooplankton and fish-growth components.  During the latter part of my Ph.D. and during my post-doctoral work I also took several extra-mural second- and third-level undergraduate courses in mathematics, statistics and computer science to augment what I had covered within my primary university education.

What outcomes from CARIM do you think there will be?

I hope that CARIM will yield an improved understanding of what environmental factors influence coastal water-quality and, in particular, how human-induced activities influence the structure, function and productivity of the coastal marine foodweb.  

I also hope that the outcomes of our work will lead to a well-informed and constructive dialogue regarding both management of our coastal marine zone and adaptation to acidification forced upon us by global climate change.

What excites you about working on this project?

This project provides me with an opportunity to work with an exciting group of people - some of whom are new to me.

The research topic has international relevance and is of economic and social import – as such  we will be required to interact with groups outside our immediate scientific peers.  This is daunting, but past experience has taught me that it is stimulating.

Alternative perspectives can lead to iterative changes to in the nature of the research that is undertaken. This can make more relevant to users’ needs and also findings are rendered more robust.