Marine Ecology Research Group

16/05/2022

In case you missed it - Some members of MERG collected eDNA samples with Smeagol DNA on our trip to the Hautai Marine Reserve in South Westland in February! There was also some red pepper DNA, but we think that was just from our lunch.

Working with mana whenua, MERG sampled multiple sites in the marine reserve so that DOC can make informed management decisions.

The extremely rare gravel maggot - named after the Lord of the Rings character - has been detected for the first time in the Hautai Marine Reserve in South Westland.

14/12/2021

Our article on the impacts of sea-level change was unexpectedly chosen as the cover story for the latest issue of GeoHazards, check it out here!

This paper evaluated impacts of sea-level change on major habitat-forming seaweeds that sustain life on rocky shores. The vertical displacement of intertidal areas uplifted by the 7.8 Mw Kaikōura earthquake was assessed using LiDAR differencing analyses from the closest terrestrial surfaces coupled...

21/10/2021

Have you ever wondered what those squishy spiral shaped things that occasionally pop up on rocky reefs throughout New Zealand are? Well wonder no more!

Believe it or not, they’re actually eggs from an extremely large species of air breathing limpet called Benhamina obliquata. This species is endemic to New Zealand (meaning it is found nowhere else in the world) and typically lays its eggs during spring. Once these eggs hatch they will release thousands of very tiny swimming larvae, which will then develop in the water column before settling back on the shore as tiny limpets.

This species is something of a seasonal rarity around Kaikōura, so our resident limpet expert (PhD student Spencer Virgin) gets very excited when he finds them!

14/10/2021

These cute little chicks are young banded dotterel/pohowera. You can see they are well camouflaged on the gravel beaches where they hatch!

Banded dotterels are classified as nationally vulnerable, and have been experiencing declining numbers for some time. Much of this decline is a result of predation by introduced mammals during nesting and fledging, when the birds are most vulnerable. Human activities can add another layer of threat to banded dotterels, as their nesting beaches often overlap with the areas where people like to walk their dogs, picnic, and drive ORVs (off-road vehicles). Photo 3 shows ORV tracks near a dotterel nest - but some nests aren't quite so lucky to be avoided.

MERG scientists have been studying the banded dotterels that nest along the Marlborough and north Canterbury coast. After the 2016 Kaikōura earthquake, there were major changes to the beaches on which the nesting grounds are found. One of our initial goals was to map the 'hotspots' (areas where nests are clustered in close proximity) to identify the most important sites to protect and monitor in the post-earthquake recovery work. Through surveys and experiments, we've also been investigating opportunities for reducing threats in practical ways. We're working to support council and community efforts to protect these birds, and helping to develop monitoring techniques that can be used to follow their fate in the years ahead.

Our initial results suggest that suitable nesting habitat expanded on the uplifted beaches, but new threats have arisen from increased ORV traffic as well. Looking ahead, protecting and monitoring the hotspots are among the key practical steps that will help ensure these birds continue to thrive following the earthquake changes.

07/10/2021

If you're able to get out for a beach walk in the next few months, you just might spot one of these little birds displaying their breeding plumage. This is the banded dotterel/pohowera, a nationally vulnerable plover species found around the beaches, river mouths, and estuaries of Aotearoa-New Zealand.

Although you might be able to spot the adults, you'll have to be very patient and lucky to find a nest! Banded dotterels are ground nesters who build their nests on gravel-dominated beaches. The male digs a scrape (a hollow in the stones) above the high tide line for the female to lay her eggs. The eggs are small and speckled, and blend in perfectly with the stony environment around them. The adults collect small sticks, pieces of seaweed, or other bits they find on the beach to place around the eggs to protect and further camouflage the nests. Check out photos 2 and 3 to see how well they blend in. Imagine trying to see them from just a few meters away!

The parents also use behaviours to protect their eggs, by running around or even faking an injury to lead predators and well-meaning beach walkers away from their nest. They return to sit on the eggs when the danger has passed. However, don't count on finding the nest by sneaking up on mom or dad - when they are sitting, they are just as hidden as the eggs. Banded dotterels are true masters of disguise!

30/09/2021

Last week we talked about the work MERG PhD student Shinae Montie is undertaking to study the effects of the 2017/2018 extreme marine heatwave on the coastal ecosystems around Kaikōura. Shinae will perform similar before-after surveys and data analyses in Western Australia to research the ecological legacy of the 2010/2011 extreme marine heatwave, this time focusing on seagrass meadows!

Shinae will estimate the percent cover of Amphibolis (see photo) and Posidonia seagrass beds around Rottnest Island, WA from high resolution satellite imagery before and after the heatwave. Satellite data will then be ground-truthed using digital imagery and surface GPS. To provide a better understanding of how this marine heatwave affected seagrass-associated animal communities she will also repeat a pre-marine heatwave sampling experiment of Amphibolis and Posidonia seagrass beds in Marmion Bay and Jurien Bay, WA. These results will inform whether community biodiversity, one decade later, in nearby reefs and seagrass meadows have recovered to support similar communities, or alternatively, if ‘warm-adapted’ species are more abundant.

Photo credit: © David Muirhead, source iNaturalist Australia. https://www.inaturalist.org/photos/34184967

24/09/2021

To determine the effects of New Zealand’s extreme marine heatwaves in 2017/18, MERG PhD student Shinae Montie will use a combination of field surveys, aerial drone photography, satellite imagery and experimental design. Part of her research includes the monitoring of 12 rocky reefs along 130 km of coastline previously dominated by the large and long-lived iconic bull kelp (Durvillaea spp.). Only one year before the 2017/18 marine heatwave, the same length of coastline experienced significant uplift following the Kaikōura earthquake, making this study area particularly unique. As we're discussed in previous posts, the uplift along the Kaikōura coast caused a massive decline in local intertidal bull kelp populations, and the cascading impact of seismic activity and extreme heating has led to an increase in smaller fast-growing seaweeds.

Shinae’s ongoing surveying, coupled with existing data, will capture successional ecological change pre-marine heatwave, immediately post-marine heatwave, and beyond. Check out the video for an example of the aerial drone surveys Shinae is using to follow these changes!

17/09/2021

How does a warming world, with stronger and longer marine heatwaves, affect coastal marine ecosystems? MERG PhD student Shinae Montie is trying to answer that question with her research into the ecological effects of two extreme marine heatwaves in Western Australia (2010/2011) and New Zealand (2017/2018 - see photo 2 for a snapshot of the sea surface temperature during this event). Her work will focus on canopy forming seagrass meadows and kelp forests, as these highly productive foundation species support a diverse range of marine communities by providing food and shelter and ameliorating stressful environmental conditions.

Over the coming years, Shinae will research seagrass and kelp species declines, local extinctions, and habitat invasions across the areas affected by these two marine heatwaves, and she will test how changes to these foundation species can have wider cascading impacts on their associated communities.

Check back next week, when we talk about just how Shinae is tackling these important questions!

10/09/2021

Bull kelp (Durvillaea spp.) populations along the Kaikōura coastline were severely affected by the uplift event following the 2016 earthquake. Many intertidal zones were left high and dry, resulting in mass die-offs of this important taonga species. More than 4 years later, bull kelp and other large brown algal species are beginning to recover, however this recovery has not come without its challenges. An eroding rocky reef and increases in marine heatwave frequency and duration are just a few of the tests facing these species.

Experiments by the MERG team have revealed just how difficult it can be to re-establish bull kelp populations.

To assist the recovery of the lost Durvillaea reefs around Kaikōura, experimental plates and rocks with juvenile bull kelp were cultured in the lab and transplanted into the intertidal zone of Omihi reef. These transplants were regularly tended by MERG scientists for several months, but they were unable to establish a self-sustaining population despite their dedicated efforts.

The pressures facing bull kelp recruits include the inundation of gravel into their habitat (Photo 2), the encroachment of other algal species (Photo 3), predation by butterfish, and a cascade of other biotic and abiotic pressures. Understanding the issues faced by these recruits illustrates just how difficult restorative efforts can be, especially in a diverse ecosystem like that found along Kaikōura’s rocky shore.

01/09/2021

New Publication Alert!

A few members of MERG have been working with NIWA to study marine heatwaves and their effect on seaweeds around Aotearoa - New Zealand. Some of their findings have recently been published in Frontiers in Marine Science.

This new paper focuses on Macrocystis pyrifera, the iconic and important foundation species commonly known as Giant Kelp. This is a highly productive species found in the shallow subtidal rocky reefs around southern New Zealand, and supplies the food and habitat that many other species depend on. The map shows the mean sea surface temperature (SST) between December 2015 and December 2020, with the known range of Macrocystis marked by the dashed red lines.

New Zealand has experienced some of the most intense marine heatwaves on record in the past 5 years. Using satellite images over this period of time, MERG and NIWA found a significant loss of Macrocystis beds during marine heatwave events, with even worse impacts in areas with poor water clarity. It may sound grim, but the optimistic side is that although we can't do much on a short timescale against warming seawater, with the right actions we CAN improve water clarity relatively quickly. If we manage to find ways to get our coastal waters clearer and cleaner, we can make a big difference in the ability of nearshore underwater forests to better cope with the expected increase of marine heatwaves.

If you'd like learn more, the full paper is freely available! Check it out here: https://www.frontiersin.org/articles/10.3389/fmars.2021.721087/full

22/08/2021

Q. Why are whitebait like chickens?

A. Because just like chicks, whitebait embryos have to breathe air inside their eggs.

These are īnanga eggs. They are about 1mm across. In this photo they are stuck to a grass stem. Inside each egg is a developing embryo. By the time it hatches (and swims out to sea), it will be 6mm long. While it is developing inside its egg, the embryo needs to breathe air because the eggs are laid so high on riverbanks they spend most of the time out of the water. The outside of the egg (chorion) needs to stay damp while the embryo develops so that fresh oxygen can diffuse into the egg and carbon dioxide can diffuse out. This is why female īnanga lay their eggs at the base of tall, dense vegetation on riverbanks. It’s a nice, cool, dark and damp place. That seems like a good reason not to disturb the vegetation in īnanga spawning sites.

15/08/2021

We often encounter seals when we are doing rocky shore fieldwork, and we always try to stay at least 20m away from them.

Usually seals aren't a problem when when we are doing whitebait spawning site surveys several kilometres from the sea - except at Goughs Bay! The locals there want to get much closer to us than 20 metres!

These are New Zealand fur seal pups.