The Royal Netherlands Institute for Sea Research
Estuarine and Delta Systems Department
Internship Report
Bivalve vulnerability to storm-induced erosion: A flume experiment
dhr. T.B. (Taylor) Craft
Supervisor: mw. L.E. (Lauren) Wiesebron Examiner: dhr. dr. K.F. (Kenneth) Rijsdijk Assessor: mw. dr. P.M. (Petra) Visser October 2020 – January 2021
Summary
The internship was conducted at the Royal Netherlands Institute for Sea Research (NIOZ) in the Estuarine and Delta Systems (EDS) department in Yerseke, The Netherlands. During the internship, a total of 75 flume experiments were conducted from mid-Oct to mid-Dec to determine the effect of erosion rates on the burrowing ability of juvenile and adult macrozoobenthic bivalves. The bivalves used in the experiment were Cerastoderma edule and Limecola balthica, which were collected in various sites throughout the Oosterschelde estuary. The erosion flume was built in early 2019 and was designed to simulate high erosion events in a controlled setting by running a water current through a channel over an upward-moving sediment core. The previous pilot projects analyzed variables such as sediment type, erosion speed, and species, but a clear relationship between bivalve size and burrowing capacity has been unclear until now. Results show a strong positive correlation between increasing bivalve size and the ability to remain burrowed for both species. These findings contribute to an increased scientific understanding of abiotic-biotic interactions in tidal systems and can be applied in modeling macrozoobenthic bivalve population dynamics following storm events.
Keywords: flume, erosion, tidal, macrozoobenthos, bivalves, Limecola balthica, Cerastoderma
Table of Contents
Summary of NIOZ and activities performed during internship ... 3
Personal Reflection ... 4
1. Background ... 5
1.1 Tidal Flats ... 5
1.2 Macrozoobenthos ... 6
1.3 Limecola balthica and Cerastoderma edule ... 6
2. Methods ... 7
2.1 Bivalve Collection ... 7
2.2 Bivalve Storage and Tidal Tank Set Up ... 8
2.3 Bivalve Burial Depths ... 9
2.4 Flume Operation ... 9 3. Results... 11 4. Conclusions ... 13 5. References ... 14 6. Appendix ... 16 6.1. Experiment Protocol ... 16
Summary of NIOZ and activities performed during internship
The Royal Netherlands Institute for Sea Research (NIOZ) is a partner institute of the Institutes Organization of the Netherlands Organization for Scientific Research (NWO-I) and is an internationally-leading marine research institution. NIOZ maintains facilities on the Wadden Sea island of Texel and the coast of the Eastern Scheldt in Yerseke. NIOZ consists of four research departments: Estuarine and Delta Systems; Coastal Systems; Ocean Systems; and Microbiology and Biogeochemistry.
This project was conducted within the Estuarine and Delta Systems (EDS) department which
“focuses on understanding the complex interactions between organisms and their physical and chemical environment in estuaries and deltas” (https://www.nioz.nl/en/about/eds). The primary work carried out during the duration of the internship supported the mission statement of EDS by testing bivalve dislodgement rates under certain conditions, thereby developing existing knowledge on how these organisms interact with their environment. Activities performed during the internship included fieldwork for bivalve collection, as well as additional fieldwork supporting other NIOZ operations, such as collecting data from tidal flat sensors, capturing photos of fixed sites in tidal flats, counting lugworm tunnels, and sieving sediment for macrozoobenthos samples.
The primary objective of the internship was to identify erosion thresholds for different size classes of two species of burrowing macrozoobenthic bivalves. The first 2 weeks of the project primarily involved testing and calibrating the flume. Although calibrations were previously performed, test runs were required to verify that the proposed experiment variables were feasible for use with the current flume settings. The current experiment differed from previous experiments by including juvenile bivalves that were as small as 6mm (shell length). Handling bivalves of this size posed a challenge that required several trial flume runs to work out and prevent future issues during the experiment. During the trial period, the availability of bivalves was tested by taking field samples throughout various sites around the Oosterschelde estuary. This was done to ensure a suitable number of specimens could be collected for use in the experiments.
After 3 weeks of refining the methodology, gathering equipment, and testing the flume, the experiment began. The daily routine differed depending on the day of the week with Mondays used to collect the bivalves (biweekly) and set up for the following week’s experiments, Tuesdays/Wednesdays/Thursdays used for running the experiments, and Fridays used to rerun any experiments that were disrupted throughout the week. Main duties included collecting and storing bivalves, operating the flume, and recording and processing data during and after the experiments. The experiments were finished in the last month of the internship just as NIOZ facilities closed in accordance with COVID-19 guidelines from the government. After the conclusion of the experiment, the main tasks included data processing, training in R programming, and writing the report.
Personal Reflection
Working as a research intern at NIOZ was a very rewarding experience. As my academic background is not directly related to marine sciences, I was able to broaden my knowledge base and develop my understanding of tidal systems, benthic species, and coastal dynamics.
Additionally, I gained insight into how research institutes operate. Although the majority of staff worked from home due to COVID-19 measures, I was still able to meet several researchers and learn about their role at NIOZ. I was pleased to hear that for the most part, duties of the research staff at NIOZ are diverse, with no two days the same.
I greatly appreciated the relatively flat organizational hierarchy at NIOZ because I was able to provide input, ask questions freely, and develop a strong sense of contribution, in lieu of performing menial tasks. My level of supervision was excellent, and I was pleased that my supervisor allowed me to develop my own methods of carrying out tasks while still proving me clear direction and encouragement. I also appreciated the balance between fieldwork, lab work, and computer work, and never felt I was trapped behind a computer throughout my internship.
As a prospective PhD candidate, this internship was particularly useful since I was able to work with and see the day-to-day work of the many PhD students at NIOZ, including my daily supervisor. My main lesson learned from my experience at NIOZ is how to plan and execute research while forecasting challenges, employing creative solutions, and standardizing processes.
1. Background
1.1 Tidal Flats
Tidal flats provide a large range of ecosystem services including habitat for migratory birds during stop-overs, coastal flood defense, and refuge for biodiversity (Bouma et al. 2014). High gradients in salinity, nutrient fluxes, and hydrology make tidal flats highly dynamic biomes with an abundance of non-linear relationships between biota and their physical environment. An in-depth examination of the highly dynamic ecological processes within tidal flats can contribute to conservation and restoration plans designed to relieve the globally-rising pressure on coastal zones. Current coastal zone management plans in the Netherlands rely heavily on elaborate hydro-engineering systems that integrate natural coastal defense systems, such as protecting and stimulating the development of coastal dunes combined with artificial barriers and man-made water catchments. Tidal flats are naturally subjected to perpetually fluctuating cycles of erosion and sedimentation but large-scale engineering projects in the Netherlands have altered the natural hydrogeomorphology by reducing sediment fluxes, changing the course of waterways, and altering natural tidal inputs. These manipulations of the physical landscape are further amplified by climate change which has led to sea-level rise and an increasing occurrence of severe storm events (Seneviratne et al. 2012), thereby reinforcing the need for large-scale coastal defense projects. As the importance of tidal flats is becoming more evident, we are also developing knowledge on how life structures, and is structured by, these important ecosystems.
1.2 Macrozoobenthos
Macrobenthic animals such as bivalves serve vital roles as ecosystem engineers in tidal flats through behaviors such as reef-building, sediment disturbance, and wave impact attenuation which protects coastlines. Additionally, many bivalve species are filter feeders capable of removing suspended material from the water and thus assist in removing pollutants from the water. Macrobenthic bivalves can also function as bioturbators through their burrowing activities, which is an essential process in intertidal zones that contributes to physical
developments such as increasing variability in sediment dynamics and fine-scale geodiversity, as well as biochemical processes such as redox reactions and creation of microhabitats (Loubere 1989). Several species of macrobenthic bivalves are also valued as a food source for humans, with the shellfish culture industry in the Netherlands harvesting over 54 million kg of shellfish in 2018, primarily consisting of oysters, mussels, and razor clams (Mol 2019). A deeper
understanding of the processes that connect infaunal macrobenthos to intertidal environments is thus beneficial to scientific researchers, shellfish culture and the greater fisheries industry, as well as natural resource managers.
While the impact of macrobenthos on sediment erodibility has been well-documented
(Wheatcroft 2006; Widdows et al. 1998; Willows et al. 1998), less is known about the effect of erosion on macrobenthos and less still on juvenile macrobenthos. This project addressed this limited understanding by using an erosion flume to determine the erosion threshold for the bivalves Limecola balthica and Cerastoderma edule. Previous flume studies measuring erosion impact have found associations between sediment size, species, bivalve size, and flow velocity (Tallqvist 2001; Jennings & Hunt 2009), but less research exists regarding juvenile bivalve resilience to erosion compared to their adult counterparts. However, previous studies have found that juveniles burrow at shallower depths (Zwarts & Wanink 1989), bivalve erosion is inversely correlated with size (Hunt 2004), and juveniles are passively transported further than adults (de Montaudouin et al. 2003; Jennings & Hunt 2009). Hunt (2004) found that the clam Mya arenaria was protected from high shear erosion velocities after a certain size reached at maturity and could only be eroded under the levels of shear erosion velocity found in storm events, whereas the smaller juveniles remained vulnerable under lower velocities. This finding implies that increased wave-current induced erosion due to climate change (Seneviratne et al. 2012) may also disproportionately impact juvenile bivalves.2
1.3 Limecola balthica and Cerastoderma edule
The tellinid bivalve Limecola (Macoma) balthica has experienced drastic declines in population in the past decade, largely attributed to a warming climate (Beukema 2009, Compton et al. 2016). L. balthica possesses dual feeding mechanisms – deposit-feeding through siphons, as well as the ability to filter feed. Suspension feeding in L. balthica has been shown to occur more often in the subtidal due to a greater abundance of suspended matter, whereas deposit-feeding occurs with greater frequency in the upper intertidal zone (Beukema et al. 2014). Deposit feeding is optimized in upper intertidal zones where reduced currents allow for the retention of benthic microphytobenthos on the sediment surface (Beukema et al. 2014). Juvenile L. balthica are known to primarily feed closer to the surface of the sediment, while adults take advantage of highly elastic and elongated siphons to feed on microphytoplankton suspended above the
sediment surface (Rossi et al. 2004). This would imply that juvenile L. balthica may be subjected to lower current velocities and concomitant sediment erosion due to chosen habitat
characteristics. Cerastoderma edule, commonly known as the Common cockle, is a bivalve species widely spread across coastal Europe (Tyler-Walters 2007) and plays an important ecological role as a bioturbator (Dairain et al. 2020) and food source for migratory birds and other animals (Malham et al. 2012). Growth rates are highly variable but overall size at maturity is significantly larger than L. balthica (Tyler-Walters 2007). Therefore, a comparative analysis of the two competing species helps us separate the connection between species, size, and burrowing ability in eroding sediment.
Figure 2: Left: C. edule (Judith Oakley, n.d) and right: L. balthica (Melisa Wong, 2011)
2. Methods
2.1 Bivalve Collection
L. balthica and C. edule were collected during low tide at various sites along the Oosterschelde
estuary (see Figure 3). Bivalve collection was performed at two-week intervals for the first 2 months of the project and required around three hours of labor to collect around 100 individuals of each species and with varying sizes. Availability of C. edule greatly surpassed that of L.
balthica, with the latter requiring the majority of the sampling effort due to the relatively lower
number of individuals, smaller sizes, and deeper burrowing depths. C. edule were primarily gathered at the Oesterdam, approximately 150-200 meters away from the shoreline. The majority of L. balthica were found just southwest of the Oesterdam and approximately 50 meters away from the shoreline, with high abundance sites occurring sporadically in patches. The bivalves were collected by hand or with sieves and stored in buckets with seawater during the
Figure 3: Map of the Oosterschelde, NIOZ, and Oesterdam. The red line indicates an area of higher L. balthica abundance.
2.2 Bivalve Storage and Tidal Tank Set Up
Collected bivalves were organized by species and size in baskets, and then stored and acclimated within specially designed tidal tanks inside a climate room set at 10° C. The tidal tanks were filled with filtered Oosterschelde water which is available on tap at NIOZ and consisted of two stacked 0.6 m3 basins connected by a pump that is activated by a six-hour timer that simulates
tidal cycles (see Figure 4). At six-hour intervals, water was pumped up from the bottom basin to the top where the water then drained, continuing the cycle. Similar to previous STORMY
experiments, bivalves were fed once weekly by dropping approximately 5 mL of filtered algae into the bottom basin which was then mixed and pumped up into the top basin.
Figure 4: Tidal tank set up. Top basin (A) drains to bottom basin (b) via drainage pipe (D) and is pumped back up with a water pump through a different pipe (C). Pump is connected to a 6-hour timer to simulate tidal cycles (Teeuw 2019).
PVC pipes (hereafter referred to as sediment cores) with a length of 30 cm and diameter of 12 cm were placed in the top basin of the tidal tanks. Before placing the sediment cores in the tank, they were capped at the bottom end and filled with 20 cm of sandy sediment which was available on-site at the NIOZ. The onsite sediment had an average grain size of 246 µm, which was
determined in a previous flume project using a Malvern Mastersizer 2000®.
2.3 Bivalve Burial Depths
To determine bivalve burial depths in the sediment core, a thread marked at defined increments was superglued to each bivalve used in the flume (see Figure 5). After the bivalve burrowed, the depth could then be determined by counting the number of mm markings visible above the sediment layer (see Figure 5). This task was conducted after the sediment cores were placed in the tank, allowing time for the sediment in the cores to settle and saturate.
Figure 5: Left: Thread marked at defined increments; right: bivalve burrowed at 3 cm into sediment. (Craft 2020)
Two bivalves of each species and size class were placed into separate cores for a total of eight cores containing a single bivalve (see Figure 6). To exclude dead/inactive specimens, only bivalves that burrowed were used in the flume. This allowed for
four flume runs each experiment day.
2.4 Flume Operation
The erosion flume “STORMY” (see Figure 7) operates by pumping water at a current velocity of 0.41 m s-1 through a network of hoses into a channel containing a hole into which a sediment
core can be placed flush with the bottom surface of the channel. To test erosion thresholds, a
Figure 6: Configuration of burrowed bivalves in sediment cores.
bivalve is allowed to burrow into the sediment core which rises upward at the desired rate with a pneumatic piston. This process pushes the sediment up and exposes the top of the sediment to the current as shown in Figure X. The upward sediment core speed simulates the erosion rate and was set for 10.7 cm hr-1 which was determined to represent a realistic erosion rate seen in natural
conditions. After the water flows over the sediment core, it enters a back basin supporting three water pumps that send water back to the front basin through hoses that run underneath the channel. After the water returns to the front basin, it is cooled by a Lauda WKL 3200 Recirculating Chiller® to mitigate heating from the pumps. Next, the water flows through a frame of PVC pipes to create a laminar flow before again passing over the sediment core.
Figure 7: STORMY Flume. I=flume channel; II=back basin with pump; III= circulation tubes; IV=sediment core; V= laminar flow frame.
The duration of an entire flume run was set for 60 mins, or until the bivalve became dislodged. A camera installed behind a plexiglass panel adjacent to the sediment core captured the activity within the flume and was used to review the exact time of dislodgement. The temperature was recorded using a HOBO® temperature logger which was placed into the flume beneath the waterline. Additionally, the water temperature was checked at the beginning and end of each flume run using a thermometer. Following each flume run, the dimensions (length/width/height) of the bivalve were recorded using a caliper, and the bivalve was placed in a vial labeled with the bivalve’s individual ID.
A log was kept that tracked the following data during, before, and after each flume run: date, ID, bivalve class (species/maturity), burial depth before placing into the flume, burial depth 15 minutes after placing into the flume, burial depth change, starting temperature, ending temperature, length, width, height, flume begin time, flume end time, total time, eroded
(Yes/No), bivalve exposure after 10, 20, 30, 40, and 50 minutes, and additional notes during the run.
II
V
I
Figure 8: Moments before dislodgement. The foot can be seen extended in the right photo in an attempt to remain anchored to the sediment (Craft 2020).
Flume runs were normally executed on Tuesday, Wednesday, and Thursday. Mondays were reserved for bivalve collection and weekly experiment preparations. Fridays were reserved to make up for any issues or interruptions that occurred during flume runs earlier in the week, as well as processing data and updating/editing the flume log.
Monday Tuesday Wednesday Thursday Friday
Collect bivalves/prepare for weekly experiments Conduct flume experiments Conduct flume experiments Conduct flume experiments Make up for disrupted experiments/process data
3. Results
Results from 77 flume experiments conducted from early November to mid-December show a strong negative correlation (r = -0.647) between bivalve size and dislodgement rate (Figure 9).
Figure 9: Dislodgement rate of different sizes of C. edule and L. balthica in an erosion flume. Smaller bivalves dislodged at significantly higher rates than larger bivalves.
Moderate to high dislodgement rates occurred primarily within the size range 6 – 14 mm with only one dislodgement occurring with bivalves larger than 14 mm. This trend of larger bivalves resisting dislodgement was detected early on in the project, so experiment efforts were
concentrated on smaller bivalves in subsequent runs. The distribution of bivalve sizes used in the project can be seen below in Figure 10 and Figure 11. C. edule displays a fairly even size range distribution from 7 – 31 mm, while the size of L. balthica ranged from 5 -18 mm with most between 6-8 mm.
Figure 10: Size class distribution of C. edule and L. balthica used in the flume experiments. Most flume runs were conducted using smaller sizes due to the lack of dislodgements at larger sizes.
Figure 11: Comparison of sizes of C. edule and L. balthica used in the flume experiments. C. edule size distribution was wider and more evenly distributed, while sizes of L. balthica were more closely distributed at smaller sizes.
Results show that L. balthica (n = 39) dislodged at a higher rate (34%) than C. edule (n = 38) at 24% (See Figure 12). While species behavior likely plays a role in dislodgement rates, this finding can also be attributed to the size differences between the two species.
Figure 12: Dislodgement rates between C. edule and L. balthica. L. balthica (34% )dislodged at a higher rate than C. edule (24%).
4. Conclusions
The role of sediment dynamics in shaping coastal ecosystems is an important research theme at NIOZ. Significant socio-ecological implications exist in this field, particularly in nations with a historically deep connection to the sea, such as the Netherlands. Data from this project contribute to expanding the existing body of knowledge on sediment dynamics by showing that adults of the bivalve species C. edule and L. balthica are better able to withstand sediment erosion set at a moderate rate in an erosion flume. These findings validate theories based on results from
5. References
Beukema J.J., Dekker R., Jansen J.M., 2009. Some like it cold: populations of the tellinid bivalve Macoma balthica (L.) suffer in various ways from a warming climate. Marine Ecology
Progress Series 384, 135–145.
Beukema J.J., Cadee G.C., Dekker R., Philippart C.J.M., 2014. Annual and spatial variability in gains of body weight in Macoma balthica (L.): Relationships with food supply and water temperature. Journal of Experimental Marine Biology and Ecology. 457, 105–112.
Bouma T.J., van Belzen J.V., Balke T., Zhu Z., Airoldi L., Blight A.J. …Herman M.J., 2014. Identifying knowledge gaps hampering application of intertidal habitats in coastal protection: Opportunities & steps to take. Coastal Engineering 87, 147-157.
Compton T.J., Bodnar W., Koolhaus A., Dekinga A., Holthuisjen S., ten Horn J., McSweeney N., van Gils J.A., Piersma T., 2016. Burrowing behavior of a deposit feeding bivalve predicts change in intertidal ecosystem state. Frontiers in Ecology and Evolution, 4, 19.
https://doi.org/10.3389/fevo.2016.00019
Dairain A., Maire O., Meynard G., Orvain F., 2020. Does parasitism influence sediment stability? Evaluation of trait-mediated effects of the trematode Bucephalus minimus on the key role of cockles Cerastoderma edule in sediment erosion dynamics. Science of The Total
Environment, 733.
de Montaudouin X., Bachelet G., Sauriau P.G., 2003. Secondary settlement of cockles Cerastoderma edule as a function of current velocity and substratum: a flume study with benthic juveniles. Hydrobiologia 503, 103–116.
Hunt H.L., 2004. Transport of juvenile clams: effects of species and sediment grain size. Journal
of Experimental Marine Biology and Ecology 312, 271– 284.
Jennings L.B., Hunt H.L., 2009. Distances of dispersal of juvenile bivalves (Mya arenaria (Linnaeus), Mercenaria
mercenaria (Linnaeus), Gemma gemma (Totten)). Journal of Experimental Marine
Biology and Ecology 376, 76–84.
Loubere P., 1989. Bioturbation and sedimentation rate control of benthic microfossil taxon abundances in surface sediments: A theoretical approach to the analysis of species microhabitats. Marine Micropaleontology, 14, 317-325.
Malham S.K., Longshaw M., (2013). A review of the infectious agents, parasites, pathogens and commensals of European cockles (Cerastoderma edule and C. glaucum). J. Mar. Biol.
Mol A., 2019. Agrimatie - Informatie over de agrosector. Visserij in Cijfers. Wageningen
University and Research. https://agrimatie.nl/?subpubid=2526.
Rossi F., Herman P.M.J., Middelburg J.J., 2004. Interspecific and intraspecific variation of d13C and d15N in deposit- and suspension feeding bivalves (Macoma balthica and Cerastoderma edule): Evidence of ontogenetic changes in feeding mode of Macoma balthica. Limnology
and Oceanography, 49(2), 408–414.
Seneviratne, S.I., Nicholls N., Easterling D., Goodess C.M., Kanae S., Kossin J… Zhang X., 2012: Changes in climate extremes and their impacts on the natural physical environment. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (IPCC). Cambridge University Press, Cambridge, UK, and New York, NY, USA, pp. 109-230.
Tallqvist M., 2001. Burrowing behaviour of the Baltic clam Macoma balthica: effects of sediment type, hypoxia and predator presence. Marine Ecology Progress Series 212, 183–191.
Tyler-Walters, H., 2007. Cerastoderma edule Common cockle. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information
Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited
27-12-2020]. Available from: https://www.marlin.ac.uk/species/detail/1384.
Wheatcroft R.A., 2006. Time-series measurements of macrobenthos abundance and sediment bioturbation intensity on a flood-dominated shelf. Progress in Oceanography 71, 88–122.
Widdows J., Brinsley M.D., Salkeld P.N., Elliot M., 1998. Use of annular flumes to determine the influence of current velocity and bivalves on material flux at the sediment-water interface.
Estuaries 21(4A), 552-559.
Willows R.I., Widdows J., Wood R.G., 1998. Influence of an infaunal bivalve on the erosion of an intertidal cohesive sediment: A flume and modeling study. Limnology and Oceanography,
43(6), 1332–1334.
Zwarts L., Wanink J., 1989. Siphon size and burying depth in deposit- and suspension-feeding benthic bivalves. Marine Biology 100, 227-240.
6. Appendix
6.1. Experiment Protocol
Task Description When Materials
Collect Bivalves
Bivalves are collected biweekly at various sites along the Eastern Schelde using both sieves and raking through sand with hands, and then placing into bucket and transporting back to NIOZ by van.
- biweekly (Monday) - bucket - sieve - waders/rubber boots
Tidal tank set up
Fill tidal tank with filtered Oosterschelde water. Place 6-hour timed water pump in bottom tank to simulate tidal cycle. Change water weekly (Thursday) and add approx. 5mL of filtered algae each week (Monday). Separate bivalves into baskets by size and species. Baskets should be placed high enough (on bricks, etc.) to be above the water line during low tide. Climate room
temperature set to 10 C. - water change (Monday) - add feed (Thursday) - tidal tank - water pump - pump timer - feed (filtered algae) - baskets - platform (bricks) - Oosterschelde water
Prepare cores Fill capped sediment cores (at least 2 for each bivalve class scheduled for the next day’s flume run) with up to 20 cm of sediment. At least 10 cm of space must be left at top of core to prevent losing sediment when placing onto piston - day prior to flume run - core (30 cm length 12 cm diameter) - blue cap - sediment - tape measure
Glue thread Spread bivalves out on a table on a paper
towel. Place several drops of superglue into small dish. Prepare thread by making black marks at 1 cm increments along the thread and red marks at 5 cm, all the way up to 10 cm. It is not necessary to mark at 1 cm increments after the first 5 cm. Total thread length should be around 15 – 20 cm. If thread is too short, it can be buried under the sediment. Excessively long thread may influence dislodgement. After thread is marked and cut, hold tip of thread against shell and apply a small amount of superglue with tweezers. Note: for small bivalves, dip the end of the thread in superglue, then apply tip to shell. Using tweezers with juveniles may result in excessive superglue. Let dry for approx. 30 mins. before placing onto
sediment core in tidal tank
- 24 hours prior to flume run - tweezers - white thread - black/red marker - scissors - small dish - bivalve - superglue - paper towel - latex gloves Inserting core into flume
Transport the core with the burrowed bivalve from the climate room to the flume using a bucket. Log the initial burial depth before inserting core. Burial depth can be determined by counting number of visible
- before operating flume - sediment core - clay - plastic plate - foam pad - work gloves
markings. As each marking is ~ 5 mm wide, more precise measurements can be made depending on how much of the marking is visible above the sediment line. Transfer core onto piston by gently wiggling the core loose from the blue cap, sliding plastic plate beneath the core, and placing onto foam pad covered with sandy clay mixture. Carry the core to the piston, with one hand underneath the core to prevent the foam pad, plastic plate, and sediment from falling through. Place the core onto the piston gently. Water may be expelled from top of core but not sediment. Jack up the piston trolley with the core aligned with the opening in the flume. Jack up until the top of the core touches the flume channel opening. Press the ‘OP SNEL’ button on the control box and hit ‘STOP’ when the sediment is flush with the flume channel.
- large box tray
Flume operation Turn on water cooler. Fill flume with water
until it reaches the 15 cm mark. HOBO should be secured to fixed point in flume. After flume is filled, wait 15 mins for bivalves to resettle into sediment. After 15 mins, check burial depth again, start video recording, turn on pumps (pump switches may need to be lifted to activate), select “OP TRAAG” on control box, record water temperature, and insert start time into log sheet. Current core speed is set to 10,7 cm/hr. At 10 min intervals, record bivalve exposure (~50% visible = exposed). Run flume for 1 hour, or until bivalve is dislodged. After the run is completed, turn off pumps, press ‘STOP’ on control box, and drain the flume until water is no longer in the channel. Remove bivalve. If dislodged, the thread should catch on the catchment area or around the bottom of the pumps. After water is drained, press “NEER SNEL” on the control box. Lower the piston trolley with the hand lever and change out sediment core. HOBO temperature data can be uploaded (weekly) by connecting to phone app and generating temperature report. - during flume run - flume - water - camera - HOBO Measure/store bivalve
Remove thread (can be reused) from bivalve. Use caliper to measure length, width, height. Place bivalve into red capped vials with ethanol. Write ID on cap.
- after flume
run
- red cap vials
- ethanol
- caliper
